lammert - 12:20 pm on Jan 22, 2008 (gmt 0)

If I understand you correctly, you are affraid that YouTube reads a text or advertisement somewhere in an uploaded video and compare it with other video's.

This might be the case, as they have some mechanisms in place to look for copyrighted materials, but they will more likely know that two different accounts are actually the same based on cookies, IP addresses and such stuff. Remember that they are now part of Google, and Google has a huge arsenal of tools to track who is doing what. Scanning texts in uploaded video's is just one of them.