[Toph]

As you can imagine, this is HIGHLY subjective. What is interesting to you may not be interesting to me and vice versa. From your Facebook example, aside from the fact that it had "huge" growth potential, I can't decipher reasons for why YOU personally found it to be the most interesting for its era. That makes it hard to quantify or recommend anything. Perhaps you can elaborate a bit more? Sorry, wish I could give a better response at this time.

[sinak]

Yeah, you're point on subjectivity is very true. I think Facebook had (and still has) quite massive societal as well as economic value. I think that's what I'm looking for. But interested to see what startups and areas are most exciting, and why..