I just noticed that players can place a computer station anywhere (not on foundation) and it doesn't despawn. Any idea how to fix it? 

Well I've fixed that with "on foundation check". Anyway I'm a bit surprised that this is a default behaviour that many kinds of entity can be just placed anywhere and forever.

They probably still don't require electricity either.   A lot of the newer items get 'forgotten' for a while after the devs first get them working.