What are the top 5 social networking sites in the US, by membership
base, how many paid and free members does each have? What is the
membership fee? Please provide the sources, which ideally should be
company-reported.
[eg Orkut, Ryze, Tribe, LinkedIn .... ]

What are the top 5 blog network sites in the US, by membership base,
how many paid and free members does each have? What is the membership
fee? Please provide the sources, which ideally should be
company-reported.
[By blog network I mean like blogger or kr.blog.yahoo.com, which is
not a US site .... ie communities of bloggers, not just bloggers using
the same software or linking independently to each other]

this is closely guarded and smoke-and-mirrors type info that companies
will keep from public view.  and for good reason... this is the
lifeblood of every single one of them.  market share is defined by how
many people are actively participating, and this drives
advertising/revenue.  this is a threat to overall prosperity, not to
mention survival.