Yea, I remember when a certain commercial developer starting with a "V" screwed up his code and because of his total control over his program forced everyone to upgrade then that took down a big part of the existing network and people started to say "Gnutella can't scale", that's how that got started.
Then Napster shut down, you think that might have been a factor in growth?
Gnutella was able to scale just fine, as it does now. Morpheus isn't using any "Ultrapeers" and seems to be doing fine with 200,000+ nodes. So Gnutella would be just about as big as it is today without the help of greed leeching off our resources and spaming us with ads and spyware.
You see, these people can't seem to stop themselves, they need to make a buck or lose their jobs. So they spam, spam, spam.
Protocol proposals came from everyone invloved, not just the commercial interests. Greed prevented some from getting used because it might not be in the best interest of profit, or controling the network/market share.

Besides, the size of the network doesn't matter after a few hundred nodes, it's the attitude of those who share. If people know their efforts arn't going to make thrid parties rich they might want to put more work into providing new and better quality content. Others may join in to add more features to the code. I don't use them but I also don't want to contribute my computer time or network resources that I pay for to third party commercial interests' pockets. I just want a choice not to.