DB Comparisons

I'm trying to decide what SQL db I should go forth with. Currently I'm developing a forum which may later on be turned into a co-branded service and if it becomes very popular, will result into some unforseen trouble if I don't choose the right DB to work with. MySQL is what I'm currently developing in, but lately, I'm hearing that very large traffic sites are having their DB corrupted and unrecoverable because they didn't back up their tables. This scares me a bit. Also, I heard that MySQL was developed ground up for speed not performance, so you loose alot of features. PostGreSQL was recommend by another because it has an excellent table locking feature so queries will be queued efficiently. Oracle was something I looked into. It's heft on the price tag, but I'm looking to port the board once I gain enough money to purchase a license. Sybase is something that are popping up in Vbulletin.com that looks promising too. Some of the boards have over 600 users logged in at once are not going down. MySQL can handle alot of concurrent users at the price of hardware upgrades. Inprise is something I'm not too familar with, but might be worth the look since it's open source and free (I believe). I'd like to know what do you think about all of these databases I mention. The features, power, hardware, cost, etc. I'd like to weigh in all the suggestions I can get before determining which way I will go. Thanks