I tried, but it was before iPhone had any kind of push notifications, live in a low population area, not a lot of my friends are early-adopter social tech types, and I'm too old to want to hang out with random people I saw on Loopt -- so, it didn't work for me. I'd be willing to give it another try.

Interestingly, in the meantime, there was a lot of foursquare adoption among friends and in the area -- enough to get network effect benefit. I don't think many of my friends have heard of Loopt.

I tried it, but found it slightly less compelling than Foursquare or FB Places (which I tried for a month of solid use); none of these services really hold my interest.

The only thing I am interested in is where my actual friends are looking at doing things in the next 0-8 hours, not where people I know from facebook are during the day. Google Latitude actually does a better job of this for me than any other service I've tried, but it's still basically useless.

Checkins were marginally useful to me in seeing where I ate lunch each day. Looking at things retrospectively was the most interesting use, and turned out to be somewhat depressing (home, gas, office, lunch across the street, office, fry's, office, datacenter, home, repeat indefinitely).

Haven't seen any Loopt activity on my social networks for a long time now. Are they in the deadpool?