This sort of thing is the MAJOR problem today.Me and my friends go to a LGS to play rather than make purchases.
Sorry to dump on you Casualcryptic but, if you are using a store's space and not making ANY type of purchase, you're definitely loitering and (it could be argued) stealing from that business. You are using up the store's resources without supporting that business and taking up gaming space that could be used to support actual paying customers.
I'm not saying you have to make huge purchases all the time (lord knows I don't have the money to do so myself @ my own FLGS!) but you should be making $5-$10 purchases of SOMETHING every time you use their gaming space. Even though i don't spend a lot of money at my FLGS, I try to donate time and energy to helping them out. A few months back, I gave them an entire table's worth of terrain I had made and just recently I've judged Ard Boyz for them.