A lot of seeds are dead and wont germinate. This happens for all plants, not just cannabis. This is why you germinate them in one place, and then plant the germinated seeds (soon to be sprouts). Otherwise you waste a lot of pots planting seeds that wont do shit. If you have a germination rate of 50%, you're doing wonderful. If someone gives you some seeds from an old shoebox from ten years ago, you're lucky if 5% - 10% of them will do anything.

Not only that, but a lot of seeds are from screwed up plants that accidentally got pollenated, or by some kid who didn't know what he was doing.

There's a world of difference between your "buddie's" seeds, and one from a reputable seed bank. Not always, but that seems to be the case more often than not.

I check mine every few hours, and the minute I see them split with the little white edge getting ready to come out, into the soil it goes. Never leave them long enough for the root to fully expose itself. After a week and a half, anything that was going to germinate would have, and beyond that, whatever seeds might come to life are pretty retarded, and I wouldn't want them anyway. Go on a picnic, dig a hole, and plant them all. Maybe one will pop to life and you'll get a chance to read about the police finding a cannabis plant in your neighborhood. :-)

In short, be happy any of them germinated, and take care of them.