If you have the means and web development experience, I would recommend that you start working on a simple replacement for Diablo 3 Trade Chat as soon as possible and start promoting it. (I'll help if it's a good webapp.)

Bashiok has recently confirmed that D3 will only have private chat, and there won't be any open or public channels. The reason for this change is to prevent player trading and linking of items, forcing them to use the Auction Houses (ideally, the Real Money Auction House.)

They're in there right now. Unless people are expecting general open channels? We've consistently said we won't have those.

Blizzard has consistently stated that they won't have general chat?

It was said once. By Bashiok. 6 MONTHS AGO. And he said Chat Channels were working and that it would be like Diablo II IRC style.

Chat channels are in, and working. They're more like the Diablo II IRC style than the individual chat windows like StarCraft II has.

Having ways for friends and acquaintances to create social groups has been in the long term plans of the new Battle.net for some time. Whether they're called clans or not is a smaller detail. It's just getting the time to work on adding in those types of want-to-have features. Almost assuredly not for the launch of the game, but hopefully at some point in the future.

This change is another method, just like the recent stash size changes, to force use of the RMAH. Even if the RMAH isn't used directly, it's still used indirectly in many cases since pro users will be purchasing Gold Auction House items, converting to gold, and then selling it for cash.

Players will still want to trade items and engage in private sales, though, to avoid costly Auction House expenses. Or maybe they just don't want to take the risk of selling a valuable item on the RMAH, and would rather trade for it.

So, grab yourself a good name (like D3XCHANGE.COM, which is currently available) and give the players something they need: a very user-friendly website where players can simply select a region to join a Trade Chat IRC-like interface. No sign-in or registration required, posts require Captcha to prevent spam, and just make it really easy for players to come and go from.

This can't be a forum, IRC, or any other kind of overcomplicated process or something requiring an third-party application. It has to be something simple and easy, just like IMGUR.COM.

It's too bad item linking isn't possible (due to Blizzard's strict no mod policy), but eventually a item DB feature could be added for easier linking.

* UPDATE (02/08/2012):

I already talked about this in the comments below, but decided to add it to the post since they're often skipped.

The thing you have to remember is that spam is not an issue these days. It's not 1998 anymore and spam is easily preventable. If you work for a large business, you've probably seen their standard spam filters at work. Even if you own a GMail account, their spam system is incredible. Out of hundreds of thousands of spam messages, 1 might make it through and even then it's flagged as spam.

Within online games, there are many ways to prevent spam. Rift, for example, locks out general chat until the player reaches a certain (low) level. Spam is hardly ever an issue, because their support team addresses it so quickly, players are banned, and the spammers need to purchase a brand new $60 game. It's not worth their time spending $60 each time.. not only does it take a lot of time to setup, they might only be able to target a few individuals before they get banned. Spammers gave up because it wasn't worth the time and investments.

And that's just one simple method. There are also player reporting thresholds if you're limited on support staff (if enough unique players report someone specifically, they can be silenced until an investigation takes place), timer restrictions or flood protection, keyword detection, player preferences (they need to manually join the channels, or they can squelch channels), chat can be unlocked using non-scripted processes (leveling, doing a quick puzzle in-game, etc.), or even captchas are available.

Spamming existing in Diablo 2 because Blizzard never really tried to prevent spamming (it was possibly a technology limitation). In D2, key generators existed where spammers could create as many CD-Keys as they wanted without any cost. Even if they were banned, it didn't matter.. they didn't need to purchase a new CD-Key and had thousands more available. Spamming was (is) fairly easy in WoW due to Blizzard's very limited support staff, trial accounts, and they fully support modding. Their only preventative spam measures were 20-year old basic flood protection algorithms. It's gotten a lot better now than how it was.

Diablo 3 is a completely different beast, though. It's smaller, easier to support, and easier to patch or upgrade with new changes. Most importantly, though, Diablo 3 does not permit mods, and Warden will be actively searching for any third-party applications that interact with the game. Automation is detected and users are banned quickly (spam being extremely easy to detect compared to character botting.) And every time they're banned, a replacement spambot will cost $60. It's absolutely not worth the spammers time or money. And even then, this is without a rudimentary spam chat filter. If they were to employ a simple level restriction (and prevent D3 demos from public communication), it would pretty much end spam.

You might think to yourself; "Well, if Blizzard allows spamming, then they could make money from these spammers since every time they get banned, they have to pay another $60." But spammers aren't idiots, they're not even going to be spamming within Diablo 3 in the first place due to the high cost of replacement involved.

Simply put, there's not going to be any spamming in the first place, so there's no need for spam protection!

So, Blizzard is removing an essential communication feature for either two purposes. It either forces trading to happen within the Auction Houses, or it's used to prevent annoying spam and improve the customer experience.

But.. there's not going to be any spam in the first place! That just leaves forced AH use.

* UPDATE (02/08/2012):

So, either we had a Real ID incident where the public outcry finally forced Blizzard to change their stance on Public Chat within Diablo 3, or Bashiok wasn't reading the forums for almost 4 days and he just now realized he made a mistake.

Blizzard is now implementing public chat within Diablo 3.

It was always there, of course, since JW already confirmed it was part of the game. Question is.. did they intend on actually turning it on, or did they wait to see what the community thought first?