In my case it's just they can call me, send a text,Why would I want people to know where I am? If they want to know they can ask.
That's sort of how I feel about it. If I'm going out, presumably I've already made plans. And if someone wants to meet up with me on short notice, they can call me, send a text, Facebook message, FB chat, AIM, Gchat, or email.
My understanding is that most people who use these things heavily are actually playing them as a game - as you check in more places, you accumulate points and... win at having a social life? I'm not sure what the objective actually is.