Both my dogs are microchipped and wear collars w/ i.d. tags at all times. The collars, of course, are NOT for leashing - I use a harness for that.
For my small guy (3 lb. adult), I do put a bell on him bc he needs to be "heard" for his safety. When he was a puppy, I would take his collar off when no one was home - then put it on immed. when we got home, so we could hear him. Once he became a little bit bigger and less vulnerable - I left the collar on at all times for add'l i.d. safety.
The deal w/ collars is that you cannot fit them according to how we fit larger dogs (the one or 2 finger clearance). You really should only be able to fit your pinky finger btwn the collar and the dog's neck. Also, I do use a breakaway collar.
