None of this was intentional. FTA:

"Update: Consumerist has updated their post with a message from Zecco claiming that it was not an April Fool's joke, but noting "Some clients may experience incorrect display of Buying Power and Account Balances." It's not entirely clear how those "incorrect displays" were apparently off by millions in some cases."

Even more important than the question of what would motivate an ISP to block services is the question of how they would go about doing it.

The FCC recently in a formal ruling that Comcast's P2P throttling was illegal and ordered them to cease and desist (see http://news.cnet.com/8301-13578_3-10004508-38.html?tag=mncol;txt for more info).

So this effectively puts a hamper on "limiting file sharing services" as a blanket policy. The RIAA will likely have to instead focus on individual users who are doing specific things. This basically just takes their problems out of the courthouse and into ISP corporate offices.