I've a reasonably full connection list on the LinkedIn contact site, and although I don't use Facebook as much as many of my friends, my list of friends there is also pretty comprehensive.
A couple of weeks ago I started to receive invitations to join friends' and colleagues' contact lists on a different service, Naymz. So I went and had a look, imported my LinkedIn contact list, and invited a few people.
And y'know, many of them replied simply: "Sorry, I'm sticking with LinkedIn, Facebook and Twitter". So I'm not going to bother with Naymz either.
I think Naymz is going to have a hard time achieving any kind of longevity, because unless I'm missing something crucial, I can't see a unique selling point. It's not unlike someone starting an online book and CD shop, or a new search engine - with the competition that's already out there one wonders where the user base will come from.