It seems like this article makes it clear that it's not really a necessity. FWIW, I've been redirected to mobile sites on several occasions just because my desk

It seems like this article makes it clear that it's not really a necessity. FWIW, I've been redirected to mobile sites on several occasions just because my desktop browser is Opera. Not that this can't be taken care of with a little careful coding, just saying that user-agent sniffing is still troublesome, and separating desktop from mobile can be tricker than expected.