What is it?

Social bookmarking community, with the last word stressed. It does't have nearly the benefits that can be achieved through Digg or some of the others, but it is more enjoyable and the conversations are engrossing.

Strengths

It is extremely well organized. The pages, groups, and profiles are interesting. There are 4 links that can be placed on the profile, plus more links can be added into the biography itself. The profile page can be made into a strong linking page with enough room for lots of content.

Weaknesses

It takes a while to get indexed often and even longer to get the links page itself indexed. You can put a ton of links on the link pages, but the ones on the profile, if it is updated regularly, are the ones that can have the most effect because the profile will be indexed more often and can gain a stronger relevance through content.

Nofollow

No nofollow yet. Until the spammers find it, it should stay that way for a while.

Conclusions

Shadow takes the mundane out of social bookmarking. There is a strong sense of internet community here, so there can be real fun in doing it. I suspect it also throws some small measure of traffic towards its sites, though nothing like going popular on Digg.