Now that MySQL is owned by Oracle, the future of the RDBMS seems uncertain. The fork by the main developer of MySQL, Monty Widenius, called MariaDB, is a drop-in replacement for MySQL. Version numbers match up of those two DB-Servers, and MariaDB will be binary compatible to MySQL at least for some versions to come. (But the way they explained that on their website, it seems those projects might diverge from one another at some point, making them incompatible).
I've build and installed MariaDB 5.2, and it looks and behaves just as MySQL. Even the binaries are called mysqld and mysql.
I heard, that it's very likely Oracle will stop releasing MySQL as a free or open-source data base system. The next logical step would be to switch to another RDBMS in time. Given that MariaDB is a fork of MySQL, it seems more than logical to use that one.
But is it smart to make the switch already? And should it really be MariaDB?
What makes me ask this question, is the project MariaDB itself. I don't want to jump to conclusions here, but is seems it's not getting much momentum. (I don't want to jump on a dying horse, if you know what I mean...)
Baron Schwarz seems to be confident that MySQL will stay solid for a while. Personally, I would not hop off the MySQL train just yet, either. Since MySQL (eh, Oracle [that just doesn't roll off the tongue, and it never will]) continues to be supported, this would give others such as Monty and Percona a chance to keep pace with MySQL's changes to MyISAM (though this might be rare). In the event ot such changes, Monty and Percona could implement corresponding changes to code for MyISAM and MariaDB.
Think of MySQL like Social Security in the USA. While there are many people speaking of Social Security eventually going away, getting out of Social Security now could rob one of the future higher monthly payouts/benfits. Drizzle went that route and froze MyISAM in time and utilizes that storage engine for temp table use only. Most seasoned Drizzle users are content with that decision, but this leaves no room for higher expectations.
So, until MySQL actually goes away, there is no sense in abandoning MySQL. Of course, by the time MariaDB is more mature and widespread, switching storage engines and DB servers is simply rendered academic and boils down to personal choice.
I can honestly relate to your concerns about the Oracle acquisition of MySQL. I have asked those same questions myself many times, and I may even come to regret my decisions to stick with Mysql. I honestly have no love for Oracle, and I think their history speaks volumes against my decision, but as it stands, it seems that the actual production of MySQL seems largely unaffected by Oracle's name being branded on top.
That being said, should something change within the MySQL product... MariaDB is similar enough that making the transition is as simple as a backup & restore. It's always nice to have that as a backup-plan.