Mongo has some pretty good performance characteristics, according to people that have very, very large datasets being updated at a massive rate. As for reliability, I personally don't really see to much difference in the reliability of Python logic vs SQL logic. It's like you're comparing the reliability of English vs Spanish.
"> Here's a neat trick - for every query SELECT * FROM TABLE, then filter and sort it in the application too."
Huh? Mongo (my personal database of choice) doesn't do that. You specify what you want when you run find(). No other database does either.
Again, if you have a point, make it. The last three posts you're written have been shoving words in to other peoples mouths, sarcasm and statements without any actual backup or citations.