How many users do Yahoo and Google toolbar and popular firefox plugins have?

[Vijay Krishnan]

I am specifically interested in getting an idea of the number of users who download these things directly, since Yahoo! and Google toolbars come bundled with other things like Y! messenger and firefox. I am basically interested in getting an idea of the number of users who would be open to installing add-ons to their browser and feel that these would give me a reasonable idea. It has been hard to find this on techcrunch and other similar sites, and I would greatly appreciate pointers that address this question.

Thanks,
Vijay