The Age of links
Which is better as a backlink?
A PR4 link that's been linking to your site for 2 years...
a PR7 link that's been linking to your site since last month?
(all other things being equal).
The days of buying links for a quick fix may be ending, and being replaced with working to obtain more "perminant" links.
A one time submission to a directory for a lifetime listing is starting to look like a nice investment right about now.