They were only given fifty keys for the WoW beta, and as far as I know that one has a lot more testers than FFXI's. Not that it's easy to tell with the NDA, but still, I'm pretty sure we'll be looking at a double-digit number of keys given out.
What does Cataclysm beta have to do with FFXIV beta other than both being betas? NA is a comparable market to Europe. The OP's assumptions make a lot of sense, as does his or her superstitious attempt to perform reverse psychology on Lady Luck.
Since SE is emulating Cataclysm's release date and beta schedule, I wouldn't at all doubt if they copied this bit too. Besides which, even if that weren't the case, the fact that they are both betas provides a baseline for how companies operate in these circumstances - much more so than simply guessing "it'll be this many". I guarantee you the number of keys is not
in the quadruple digits, that's for sure.
Yog does make a fair point in terms of population proportions, though. However, given the proportional difference versus the absolute difference, it's still quite unlikely that we'll see more than 50-100 keys given out.
ETA: And I don't know what the NA vs EU bit is supposed to mean, since SE's contest is NA only and I think WoW's was NA/EU (could be mistaken). Unless you're referring to how many the German site gave away, which would make a reasonable baseline and which I originally missed. "Between 500-5000" is a **** of a range, though, and could be predicated on a different system than ours. Edited, Aug 9th 2010 10:58pm by Majivo