[eluser]Michael Wales[/eluser]
Probably not the best, security-wise, but I just use the same username/password for the entire database (with each application on my server receiving one database).
This is a pretty common scenario within the shared hosting world as well as in open source PHP projects. Really, the only chance you have of someone getting your username/password is if your server is misconfigured and they can view your configuration files.
I did have one project, that I did for work, that we used multiple users. It was a "For Sale Board" that we wanted people on-base to be able to read/write and people off base to only read. Since this was running across a DoD network, with a waiver to punch a hole in the firewall for the database connection, we were extra careful in that scenario.
It really wasn't necessary - but, worst case scenario if someone managed to view the source they would simply see the read account's information.