The particular property/behavior in question is the now-AOL-owned Huffington Post. The HuffPo is sometimes criticized for being "just" an aggregator, but regardless it's widely understood that HuffPo has had problems with people critiquing how much of a story it has used. As techdirt points out, in the past the HuffPo has taken all of an article it is aggregating and added its own value, claiming that the result is fair use.

Well and good, so why are AOL's lawyers now hitting a small-town blogger with cease-and-desist letters for that blogger doing pretty much exactly (to AOL's hyperlocal Patch) what HuffPo did to others? C'mon, guys either it's fair use or it isn't. You can't both claim fair use when you're doing it to other people, and infringement when others do it to you (well, unless you're Disney and Hollywood studios in general, a matter in the queue for next week).