In distributable software, I dont want my customers mucking about in the database by themselves. The program reads and writes it all by itself. The only reason for a user to touch the DB file is to take a backup copy. Therefore I have named it whatever_records.db
The simple .db extension tells the user that it is a binary data file and that's all they have to know. Calling it .sqlite invites the interested user to open it up and mess something up!
Totally depends on your usage scenario I suppose.
