There's a BIG difference in Pitchfork/tumblr and this article where the author had @digg on Twitter where he/she displayed data from Digg's RSS feed. This big

There's a BIG difference in Pitchfork/tumblr and this article where the author had @digg on Twitter where he/she displayed data from Digg's RSS feed. This big difference is the tumblr guy was not infringing on Pitchfork's trademark while this guy was. If Joe's Apple Farm has @apple or apple.tumblr.com, he should be able to keep it if he has non-infringing content where he talks about the apples he grows. If Joe starts displaying iPod affiliate links and blogging about iPads, he has crossed the line into a situation where he may be infringing on trademarks.