Facebook Inc. received what may be its first "sell" rating on Friday, from Pivotal Research Group, which also set a target price of $30 for the stock.

Shares in the No. 1 social network fizzled in their debut on Friday, managing an 18 percent gain before backtracking to trade close to their $38 initial public offering price.

"We are wary of the disconnect between revenue growth and operating/capital expense growth expectations," Pivotal analyst Brian Wieser said in a research note.

"The market is pricing Facebook as a less risky asset than Google, which we believe is simply not the case."