Using sqlite as the "this is just an idea" phase positions you better for scale-out/build-up if it becomes necessary. Helps keep your head straight but doesn't slow you down.
I say this as someone who worships Crockford for inventing JSON.
I've seen too many projects get fucked hard because they used flatfiles.
Edit: Seriously though, managing synchronization/atomic changes to flatfiles manually is a Bad Idea (TM).
It's somewhere up there with, "I have a performance problem. I'll use pthreads!" Now you have 1,02-SEGMENTATION FAULT problems.
Like I said, in my case there were no changes, I only read from them. So I let the server cache the hell out of them and the entire site was fast because of it.
I say this as someone who worships Crockford for inventing JSON.
I've seen too many projects get fucked hard because they used flatfiles.
Edit: Seriously though, managing synchronization/atomic changes to flatfiles manually is a Bad Idea (TM).
It's somewhere up there with, "I have a performance problem. I'll use pthreads!" Now you have 1,02-SEGMENTATION FAULT problems.