Actually my friend and I were just talking about this at work the toher day. My dogs are fairly big (50+ lbs) and she has two GSD and one good size mix. All the dogs are super freindly and would never hurt anyone. But becuase they are big, they are scary to some people. And yes, if you don't know the dog I can understand why. But, as KayAnn said, little dogs can be just as mean. My friends parents have a chiuhuahua that doesn't like many people. No one thinks of a cute little chi or poodle as mean, and most aren't, but I have met more mean "toy" size dogs then I have big dogs. Maybe I have just been lucky to not meet a lot of mean dogs at all.
I think in general, whatever size dog you have, do the best you can to keep it solicalized with dogs and people, let people know your dog is friendly, if you can. And although dogs get out accidently (mine have too), keep them on a leash other times. I have seen too many people let the dogs run loose and are schocked when you don't like them running up to your dog, not knowing how either dog will
behave. My dogs love other dogs, but not all dogs do.

Aas a result of our dissucsion at work we thought may it would be a good idea to carry a water bottle when taking walks. Many people use this to correct their dogs. we thought it may be better used to correct owners And I don't mean the one whose dogs accidently get out, but the ones who knowingly let their dogs run lose or don't seem to care when you bring their dog home from 3 blocks away...Can you imagine spraying someone who is letting their dog run down the street a head of them, "Bad Owner" Squirt, Squirt