There is already a big market open for business for +1's. I bought some for a site just to see what happens, can get pretty much unlimited amounts for pretty cheap.. Will be interesting to see if it help with serps.
With all the years of experience, Google has, I think they have systems to give each +1 a value in the same way, they give each link a value.
The link from the PR 8 site with related theme, the link from the PR 1 site complete unrelated.
The link from the PR 8 site from an university to a gambling site ;)