more than 9?

[Eruanna]

I agree that the Elves made the rings for themselves. Their purpose seems to have been for good. Elrond says:

"The Three were not made ... as weapons of war or conquest: that is not their power. Those who made them did not desire strength or domination or hoarded wealth, but understanding, making, and healing, to preserve all things unstained."

'Preserve all things unstained' this seems to be the crux of the matter. To keep Middle-earth stable and unchanged. Estelyn's question is an interesting one. What may have happened if the Elves had been able to keep their rings? A society that does not progress will stagnate and die.

I don't agree, however that the Seven and the Nine were the most powerful of the rings. Sauron had already gained possession of the Nine when he captured Celebrimbor and tortured him into revealing the whereabouts of the remaining rings.

Then Celebrimbor was put to torment, and Sauron learned from him where the Seven were bestowed. This Celebrimbor revealed, because neither the Seven nor the Nine did he value as he valued the Three." Unfinished Tales : The History of Galadriel and Celeborn

These three rings are elementals, of sorts, and certainly seem to be regarded, by the Elves at least, as more powerful than the others. Or perhaps I am reading too much into this and it is simply the fact that the Three were untainted by Sauron that makes them so special to the Elves.