I've never discouraged my dog from interacting with other dogs. There have always been other dogs around her, in the park, when she went to training classes, my DD's dog. She's just never been particularly interested in any of them, except, as I said in my pp, just the odd one or two.
Actually, thinking about it now the friendships she did make in the past with other dogs seemed to be quite strong and she'd always be really happy to see those particular dogs. As she's got older she tends not to make friends with other dogs in the same way.
She's calm, confident and happy and loves meeting all sorts of people. And she's probably the least aggressive dog you could wish to meet.
I think, as with humans, the amount of need a dog has to interact with it's own kind is probably governed by personality to a great extent.