Using a single database for all my domains

Does it really matter if i create/use just ONE SINGLE database for all my hosted domain sites or create/use ONE FOR EACH domain site?

i just need to know if using a single database can cause a negative effect on my shared hosting account.

here’s a sample setup:
setup A: 100 domains using just a single database

setup B:
1st set: 50 domains using a single database
2nd set: 50 domains using another database

setup C:
All 100 domains uses different database.

The most negative effect is that it’s harder to weed through the database to do maintenance. There’s no good reason to put everything into one database. You get unlimited databases, so why not use them?

Oh, and another negative effect. If one of your sites gets compromised, the intruder gets access to all of your data.