There are plenty of ground breaking apps but they aren't making billions of advertising revenue, nor do they have large numbers. I honestly think torrent applications (and most peer to peer type of stuff) are very cool and very useful for small-medium groups but it'll never scale to a billion user thing.

Do agree it's a weird metric to have, but can't think of a better one outside of "business" but that still seems like a poor rubric because the vast majority of people care about things that aren't businesses and if this "life altering" technology basically amounts to creating digital slaves then maybe we as a species shouldn't explore the stars.