Homenet nailed it.
Those are the sites I recommend in an ebook I wrote.
Most will be do follow... I believe squidoo has some issues if you don't get enough visits or something. Hubpages is like that too.
10?
Do a bunch more than that.
My typical set up when I am promoting a site is around 30 per keyword with ezine as the base.
When you say ezine as a base, do you mean one ezine article that you drive all the other web 2.0 traffic to or do you mean the majority of those 30 sites would be ezine articles?
Also, if I setup a wetpaint site and put an article on that site, is it best to create a whole new wetpaint site to add another article to or should I just add another page/post to the wetpaint site?