http://googlewebmastercentral.blogspot. ... input.html
There is some speculation as to what exactly constitutes a paid link.
As the PO article said...
Always remember, Google doesn't need to be fair or reasonable about these sort of things. It's their index—we just play in it, and spam is what Google says it is.
In other words, it's one more way they are covering themselves. Expect a variable implementation policy, as these things are definitely not written in stone.
For any subscribers who missed it, here's a link...
http://www.searchenginenews.com/se-news ... tml#GOOGLE