I think
you should consider money and power before deciding on your database. Some databases are definitely more expensive then others whereas some allow a lot more power, especially in distributed computing.
For example, Oracle is usually more expensive than SQL Server, but often more powerful (although I haven't checked pricing and new features lately so this could be out of date). Then again, if you aren't in a situation where you don't need the power, then you're throwing your money away where you don't need to.
Chances are if you don't know what you want to use, go with MySQL for now since it will save you a lot of money. IBM's Cloudscape database recently became an open source project, although I don't know too many people using it other than to manage WebSphere queues, so it probably has its own pluses/minuses.
[ November 27, 2005: Message edited by: Scott Selikoff ]