I've seen that sentiment a lot, and I'm not buying it. Whatever you think of their individual politics, no reporter who wants to remain in the profession is going to burn a source as big as Karl Rove.
And it's bigger than Rove alone -- if they gave up an anonymous source, they'd have no luck finding anonymous sources in the future.
If O'Donnell's words are false, does that open Rove to a libel suit or defamtion of character suit for saying he committed perjury?