You seen the licencing costs on the real thing-Oracle or MS?
Gox's profits of the last 3 months could be blown on a few MS Enterprise licences. Tho Enterprise isn't worth it
MySql can do the job just as well......but only as good as the person who implements it and the models they use.
TBH....DB is old tech, some of the tech currently in development will make traditional relational databases look like a Model T.
Yes, that's valid logic when setting up a website for something like ... your favorite anime movies.
But if you're considering setup of a site that deals with lots of $$$ and has to interface with a large user base ... and needs to be secure ... here's what you do:
1. Get some investors to fund your project
2. Spend the money on real database technology
Actually, the above model is true for anything that aims to be even remotely professional. There is no comparison between MySQL and Oracle. I've worked with both on a professional level and several others who have gone the way of the dodo (eg., Sybase, Redbrick, etc...) including performance bench-testing them all.
MySQL would have been fine when they were trading a couple of thousand $ per day. It's not fine anymore.
But you don't have to believe me. Time will tell the truth beyond the shadow of a doubt.