Not having a go or anything, but I don't understand why people feel the need to say hello to every famous person they see. I'd never do it, just out of respect for other peoples privacy. Imagine it the other way round, having people come up to you every five minutes while you are trying to get on with stuff.
I saw Lionel Blair once and said fuck all
If I like someone's work then I smile and thank them.
Not stalking, not after an autograph, not swooning all over people.