I agree that it happens to most of us BUT I agree with Midori - you should always apologise.
It infuriates me when people watch their dog bound over to "play", or stand there shouting "He won't hurt you, he's only a puppy/just wants to say hello" or whatever.
If they make an effort to get the dog back, and/or apologise, I don't mind a bit. Nobody's infallible.
I've been on the other end loads of times in the early days with my dog, but I always apologised profusely. In fact at times it would have been easier if people were LESS friendly - it's really annoying when you're trying to recall your dog and someone's going "Oh, it's OK! I don't mind him jumping up! Hello! Ooh have a treat...." etc
On one occasion I was walking down a fairly narrow path through the woods and my dog was among the trees chasing squirrels. Coming the other way was a woman with a small fluffy thing on a lead. My dog emerged from the woods right where the woman and dog were, and sniffed the little dog nicely. The little dog sniffed nicely back. All happy and fine. Whereupon the woman GRABBED her dog and swooped it up into the air, causing it to emit a startled squeak.
This, in effect, turned the small fluffy dog from a dog into a small, fluffy squeaky toy, given that the woman was sort of waving it around. So my dog stood on her hind legs to sniff it some more. Whereupon the woman kicked out at my dog.
It all happened so quickly, and my dog came away as soon as I'd gathered my wits enough to call her. Fault on both sides I guess; possibly I should have called her to me from the woods as soon as I spotted the other lady approaching, just in case... but I didn't think she'd emerge at precisely the moment they passed. But I still think the other woman overreacted massively. Her dog seemed absolutely fine with other dogs but I'd guess, if she's still picking it up when another dog comes near, it isn't any more :(