MySQL?

A few weeks ago I got the last aisle seat in the plane as an earlier flight was late and there were some available seats. The advantage of the last aisle seat is that going to restroom is never an issue. Just free to go anytime. The second, its an observer seat. And so was it as I found one over zealous Marketing professional from Sun Microsystems sitting diagonally opposite to me. He was reading a presentation he might have attended that caught my curiosity as I saw one funny line Keep promoting MySQL to the customers and of course other interesting statements. Now, with MySQL's acquisition I guess that "plan" is taking affect.
So what actually does it mean to offer a database? Barring very high performance databases like Oracle or DB2, does it really matter if you use MySQL, Postgress or SQLite in the back-end? Who cares what the database is if all your data resides in a Grid like Coherence? The best feature offered by your database can be done in a fraction of a time in the Grid.