Google Analytics has currently 237,021 accounts -- 241 more than my last post. I've had a few comments asking me how I got this information, and a whole group of diggers asking the same question. I would be happy to share that information with you.
If you log into your Google Analytics account and click on a report, you will notice that the query string looks similar to https://www.google.com/analytics/home/report?rid=xxxxxx. The query string variable "rid" is the one that specifies your account ID -- if you change it, it gives you an error message.
Try using 50000 for the rid and you will see an error message that says "Could not...". That error message is slightly different than the one you get when you try 1000000 which says "Failed to...". Simply find the point at where the message changes from "Could not..." to "Failed to..." and you've found the magic number.