KnowEm is the latest in services that check for unclaimed user names at multiple social sites. This is helpful if you're interested in retaining the same user name at sites you haven't yet signed up for, or if you're on the verge of launching a new site or service and want to lock down that brand name before someone else does.
Most recently we checked out Namechk, which does the same thing for 84 different sites. KnowEm steps it up by searching in 120 places, as well as offering a premium service which will actually go to each site and sign you up. This doesn't come cheap though; it's $64.95, and it only goes to the sites where the user name is still available. It then sends the log-in information back to you so you can do things like change the password and where it's sending confirmation e-mails.
What's more, is that for $10 a month it can keep signing you up for any new services it adds to its search engine. It promises anywhere from 6 to 10 per month, but that can change depending on what new sites are introduced during that time.
Is it worth it to place your money, and trust in a service like this? It depends on how fast the providers are at adding the new sites and registering for you. If you've got an eccentric, or otherwise uncommon user name then yes, it will probably still be available. However, for more common names, you're better off keeping an eagle eye on your RSS reader and signing up for new services as soon as they're announced.