How does Google match an account to you?

A couple weeks back I was asking how Google found out my Twitter account went with my Google account. Their explanation:

"Google uses two primary signals to make an educated guess about which public accounts you may own:

Similarities between your Google Account name and usernames, and other account names and profile names. For instance, Bob's Gmail address is surferguybob@gmail.com and his Twitter profile name is surferguybob.

Similarities between your connections. For example, Bob's Google Contacts have names that are very similar to the names of people he follows publicly on Twitter."

http://www.google.com/support/websearch/bin/answer.py?hl=en&answer=1142745