*sigh* No Storm.
Though it's possible I'm incorrect in saying this, I'm 99% sure I'm not.
We will never over take/stop using Source's normal ban system, which, sometimes unfortunately, is a straight text file called banned_user.cfg
The main reasons we use an additional file now, and it's the bans.txt one are;
1) "Temporary" across multi-session - Source bans don't keep "temporary bans" across server sessions. If you temporary ban someone using Source, no ULib loaded, for 5 days and your server restarts for any reason before that 5 days is up, that ban is gone. With our file, it will stay until expired.
2) Reason tracking
3) Who tracking (both name banned, and who did it)
4) Others I now forget.
If/when we start storing OUR ban information in a new format, be it SQLite or whatever, as Megiddo stated, he plans on converting whatever is in OUR bans.txt file.
The Source bans file would still be loaded as normal, and perhaps, given our industrious nature, also as an addition be stored in a separate sqlite db file.