LinkedIn is getting rather large. Yesterday evening, the network's vice president of marketing announced on Twitter that it had hit a milestone in terms of users, attracting its 60 millionth member. LinkedIn had just 55 million members as of December 17th, so this new declaration means it's grown by a little more than nine percent in less than two months (which translates to a rate of at least 109 percent per year). That increase in size is, it should be needless to say,