Andrew has already spoken to the single writer matter. Another issue is it's not very easy to scale horizontally at all. You could shard, but you're not going to be doing replication very easily (although a project
does exist to provide replicated SQLite -
https://github.com/rqlite/rqlite - but then you might as well finally use Postgres or whatever).
My attitude to this is if my project can be working well and turning a profit within SQLite's limitations, we can worry about migrating to a different stack later on. The same reason I use Ruby for almost everything initially too.
