Common isn't the word for it. The fake porn profile is de rigueur for Myspace. Expect any median to high profile porn ho to have anywhere from 3 to a dozen profiles... none of which may be authentic.
Although they're a pain in the ass, I was mildly amused by the young man who posed as Mika Tan on Myspace... then outted himself, and proceeded to gleefully denounce the Mika fans that had added him as "degenerates" and "perverts" [ 'cuz, ya know, there's nothing perverse about a white guy posing as a diminutive Asian woman ].