Many many times. The problem comes from management being paranoid about crew having some sort of control over what happens to their aircraft once on the ground. A snag in the book is a very powerful veto on their planning. There is no real answer to this. How many times have we heard " If you won't take it, I'll find a crew that will" or to a ground engineer "If you won't sign it I'll get someone that will". I just think we have to do our best to demonstrate that the tech log is a line of communication with maintenance. If you are sufficiently qualified, it is a good idea to write snags and transfer to 'B' defects at the same time where you can. It shows that you are not trying to deck the aircraft, but use the system as it is intended.
There is no such thing as a verbal snag.