> Don't use monogdb unless you know what your doing
That can just as well be applied to anything, not just mongodb. Whenever you start using something, you're going to make mistakes.
> and have the hardware to do it right.
AFAIK, running it on two instances (master + slave, and then stop/cycle the slave for backups) should be just fine. So you don't need to have "web scale" hardware for mongodb.
MongoDB is an interesting database and can fit nicely into some use cases - by which I mean data organisation, not just scale. So I don't think it should be avoided by people running simple things with not-humongous data-sets. We just have to look out for a few things we might not have expected. That's why I didn't call them "bugs" or "problems" - just "gotchas".