Why did Blink fail?

Blink.com started in 1999 was one of the earliest social bookmarking site founded, they were 5 years earlier than de.licio.us. They had bookmarking under folders like this:

Blink had started way ahead, had great staff, had USD 13M in funding. But failed to make the impact that delicious did much later, delicious was acquired by Yahoo for USD 27M.

So why did Blink fail? Ari Paparo founder of Blink had a post on this after the delicious acquisition.

I found this point made in a comment the most relevant:
Implement to solve a single problem, trying to do too much will cause failure; and be clear on the problem you want to solve.