Increased hiring made sure users are active on LinkedIn. Together, the networking site's subscribers paid $568 million for services in the past three months. That's more than what was expected. Consequently, the site reported a profit of 52 cents a share, a nickel above estimates. LinkedIn has over 300 million users. Most of them are white collar professionals who take their careers seriously. However, it's questionable whether the networking site can keep the user engagement level up. LinkedIn said it worries that hiring will slow down between now and year end and some users might leave.