I requested an issue on here a few days ago and also got some great solutions, i am considering carrying out a facebook style website with profiles, bio's, etc, and requested whether i ought to use mysql, the solutions would use Cassandra because its far better. I am just asking is what everybody indicate, its just i understand mysql fairly well and will it be a totally stupid move ahead my part to make use of mysql over Cassandra (that we hadnt even heard about until a couple of days ago)
Choose MySQL. Cassandra can make development hard, still it lacks tools, lessons, etc. And it is quickly altering, so you will need to improve your code too.
Have a look at this article - it describes why I believe it's not time for normal projects to choose Cassandra.
Just in case the application sky-rockets and requires more scalability than MySQL provides, then you will have sufficient people to handle transition to Cassandra. Just abstract your Data access layer to ensure that you are able to later switch without altering the relaxation from the code.
Update: Note the date of the answer. It's obviously going to get away from date, check if you will find already good tools, lessons, etc.