I'm posting here as Chapper referred me to this thread after reading one I'd started about seeing people who just root you to the spot and make you feel funny... it happened to me very recently (see the "woman in Waitrose" thread) and while I bathed in her beauty for a few minutes I would, for various reasons, never think of just going up to her and asking her out.
A few years ago though, a similar thing happened in a shop and there were a number of very good reasons why I could quite easily have approached the woman - and to top it off, she kind of hung about outside afterwards, looking at me. I occasionally wonder why I didn't do or say anything, and what would have happened if I had - what direction my life would have taken. Oh well. Perhaps there's an alternative me that did, and is living a different life as a result.