Must-read post by Ari Paparo on why older shared bookmarking services such as his own Blink didn't work out as well as the much more recent and less-funded del.icio.us:

"[P]roduct design matters. We had more money, more users, a five year head start, and some really, really smart people working on bookmarking in 1999. The bottom line is that we simply didn’t get it right. Some simple innovations like using tags instead of folders, making public the default, building better discovery features, etc made the difference between being an also-ran and a hot acquisition target."

Meanwhile, David Galbraith looks at the damage done by raising too much money.