I was originally applying to social psychology programs where, as someone mentioned above, its basically a necessity to email professors to make sure they're taking students. When I decided to switch to sociology, I emailed a few professors at my top schools and was basically met with a "huh? why are you emailing me? I'm sure we will get to meet if you're accepted." kind of responses so I stopped emailing. One caveat is that I noticed on the UCI app they ask if you've had correspondence with anyone and want the names. Soooooooo I don't know if I should leave that blank or last minute email the professors whose work I'm most interested in.