Glitch is a wonderfully social game but sometimes you just aren't in the mood to chat with half the world or more often you want to spend some time uninterrupted while talking to just one or two people. It's really difficult to have any sort of real conversation with somebody when you just keep getting PMs from all sorts of different people.
It would be nice to be able to either have the option to hide your online status or at least to make it so that there are places you can go hang out privately. Perhaps add the option to your house or make the hidden streets truly off the grid.
I know there is a block button but that is just not something you use on people you consider friendly acquaintances. It would hurt their feelings which is just a very uncool thing to do.