Earlier quoted context omitted.
Flask is used by Pinterest and LinkedIn, which I'm guessing are a touch more than 100 lines of code. Flask is, of course, more powerful than bottle, and has less batteries included than Django. Saying Flask is good for 100 LOC sites is terrible advice, no matter which way you try to slice it. It isn't. It's widely-used and well-maintained. Don't get me wrong, I like Django as well.
I've used Flask for single file sites with 10-250 lines. It's great (ish). What's bad about it? Your saying it's only good for writing large applications? How so?
Django is no different. Django falls apart spectacularly in the hands of people who can't program.