If bcrypt isn't an option, you straight-up need a better platform. It's inexcusable to refuse to protect your users--if you're not using bcrypt/scrypt/PKBDF2 you're mistreating your users.
The fact that they're big doesn't mean they're right, of course. But I know I've seen a bunch of news stories about DB leaking and I haven't seem a bunch about the source code to the website leaking. (Obviously there is some confirmation bias there.)
For the 99% case, 'pepper's are illusory security.
And you should still be using bcrypt. (Or PKBDF2, or scrypt, whatever. Just not something where a "pepper" actually ends up mattering.)
As I said, you can't use any of these on Google App Engine. They're not provided by the platform, and you can't upload them yourself because they use C.
And 'peppers' don't do anything of significant value in such an environment, either, because your app's going to get owned before your database is.
Citation needed. There appears to be a case where it could prove to be an advantage: http://security.stackexchange.com/questions/3272/password-ha...
> And you should be using bcrypt anyway.
Yeah, except bcrypt isn't always an option. Eg: on Google App Engine.