What do you guys do when you have to go use the restroom facilities? I tend to bring my laptop in with me since the loss of it would piss me off more than the embarrassment of taking it with me.
Scope the place out, try to sit away from doors, leave my jacket, throw my laptop in a sleeve and take it with me. I would never leave a laptop on its own.
I always just leave it out and go to the restroom. Maybe some would call that foolish, but I'm not too worried about it. It seems like everyone at the coffee shops I go to already has their own laptop that is better than mine anyways :).
I have asked someone to ask my laptop after sitting with the same people for a while and/or they have asked me to watch theirs - in a kind of tenuous, reciprocal agreement. However, most times I feel it's not worth the effort.
I try to find a seat close to the restroom and generally just leave my laptop there (with the screen saver lock on). The way I see it, it usually takes me under 35 seconds to take a leak: 10 seconds to get up and walk into the bathroom and 15-20 seconds to take a leak. Sitting in a long coffee shop, far from the entrance, that really doesn't give someone much time to swipe my laptop without me seeing them.
Plus, if others around me have seen me there long enough, I feel like they'll point out who/where the thief went when I come back out. You also just need to use your judgment. I'd never leave it there in an unfamiliar coffee shop or if I planned to be gone for more than 40 seconds.
You have to ask someone to watch your laptop. I'm a psych major, and there was a study that demonstrated that people have a _much_ higher rate of deterring thieves when asked to look after someone's items, for some reason.
Or, get a laptop with built in GPS and 3G internet, and hack the firmware to autoemail you the location on boot-up.