I know several people, as well as myself, who are head-hunted reguarily on linked in, and have seen multiple job offers come across this table. All in all, it's not bad. But more importantly, if you've been a part of a big company and worked across teams, then keeping track of all those aquaintances is valuable - they might be your 'in' to finding a job again some day. In that regard, it is near priceless.. I don't want the other software devs on my facebook, but I do want to keep in touch.