In some genres (romance comes to mind, but is not the only one), most novels are written by people of one sex. So a novelist may take a pseudonym of the opposite sex if he (or she) desires to write in that genre. Obviously, personal appearances are out in that case. So what's an author to do who swims against the tide? Stick to blogs and e-mail interviews?
Well, no one is all that shocked that the editor at Beatrice.com is a man. Or that ChekhovsMistress blogger is a man. Or that Miss Snark is a man...wait, that's not quite as humorous as I thought it would be.
The idea of a grizzled, fedora-wearing, cigar chomping Lou Grant writing romances as Fifi LaFemme is pretty funny but I bet the girls over at Romance Writers of America would get a kick out of it. Heck, there are so many girls at those conventions that a man, even in a fedora, would be kind of fun.
I don't think writing as the "wrong" gender precludes much of anything. Heck in this day and age, even dogs and cats write books and no one blinks an eye when humans show up to do the author talk.