Users of the Google Affiliate Network can now access the network through a regular Google account. This means uses will be able to access Google's other products like AdWords, AdSense, Gmail, Google Docs, Google Calendar, etc. with the same log-in.
For now, Google Affiliate Network users still have the option to continue using their existing log-ins. In fact, Google will not be updating the Affiliate Network Sign-in pages until all users have updated. Once a user updates their Account, they'll no longer be able to use their old Google Affiliate Network username and password.
It seems like an interesting way to get more people signed up for real Google accounts. It could prove to increase the amount of use of other Google products, as I'm sure that's the idea.