Well, I guess I will have to be the voice of dissention on this point, as I feel anyone who is using bookmarking solely to generate backlinks must be totally missing the point.
To me, no matter what your SEO strategy looks like on paper, or in design it always has the end-goal of increasing traffic. In fact, contrary to what everyone else is saying, I use bookmarking to grab traffic.
When you can identify hot trending topics, and you post content to a solid base point such as a blogger, hubpages, squidoo, or your own authority site, what you can often find is that bookmarking those drives their immediate search engine placement up, and you can snag A LOT of traffic. Obviously it's less effective on long-term expected trends.
I wouldn't recommend using ONLY bookmarking as your SEO vehicle, unless you ONLY target keywords the way I've suggested above, and of course - it's short-term money. But hey - short term $100+ days add up quite nicely too.
Do some long-term stuff though too.