Where is the line in the sand (for you) between an employee doing something a little 'grey/funny' and doing something that you think they should get the sack for?
Have you ever been in a position where you have witnessed behavior you think has crossed the line? If the person was a colleague did you 'dob' on them? If you were the boss did you sack them?
For me (and yes each person is going to be different) I don't bat an eyelid at the occasional phone call or photocopying for personal use... As long as it's not excessive and/or regular (eg 40 pages every few days for study or calling std and chatting with Nanna for 20 minutes every couple of days). If I witnessed someone being excessive I would probably say something to them like "you're bold doing that hoping you won't get caught." If they continued to do it I would Dob or formally counsel them if they were my employee.
With regards to physical property. For some reason I am turned off at the thought of people intentionally taking physical things from the workplace home for personal use (stationary, supplies etc). Accidentally taking a pen or rubber home and keeping it there - meh. Intentionally raiding the supply cupboard on a semi regular basis - not ok. I would counsel an employee I caught taking stuff (or tell their supervisor if it wasn't me). If it was a significant amount of goods (money and/or amount wise) I would like to see then sacked.
Messing with the integrity of confidential work information (including client information - looking it up for personal jollies etc) is something I have no tolerance for. If I caught my employees looking up confidential client information when they didn't have a need to know I would like to think they would get the sack (and depending on the nature of the offence criminal charges laid).
In reality there aren't that many dodgy people where I work...(that I know of!). I once heard (third hand) a story that one employee had trifled through people's draws when the office was empty reading managements performance reports on others. I didn't feel comfortable 'dobbing' as I heard the information third hand and wasn't sure about its accuracy. If I witnessed it myself/first hand then I would definitely out them, and campaign for a formal warning if not the sack.