Matt Cutts quite awhile back announced a modification to the way the PR was allocated, etal., so that now:
- The source page's PR is first divided equally among all links, without regard to the target URL or the presence/absence of "nofollow;"
- Of multiple links pointing to the same URL, all but one, along with their shares of PR, are discarded; and,
- All "nofollow" links, along with their shares of PR, are discarded.
The purpose of this was to nullify the practice of "PR sculpting." The result, of course, is that some of a page's available PR may go unused.
Various 3rd party tests, using different anchor text on multiple OBLs pointing to the same target URL, have found that it is the first such link that is indexed. Those same tests also determined that, even if such 1st link bears "nofollow," if its target URL was previously indexed, it too is indexed.