This doesn't help me, Fonglh, thanks for your answer though.
I know that it is possible to "shard". Which apparently means running an installation over several databases on different servers. But does sharding mean that each database has the same data, or can they each house a different table?
If it is possible to have each database hold a different table, (or tables,) then it seems to me that each database would hold less data than the sum of all of them? Right?
And finally, would it be possible to have all of those databases on the same server? (The tech guy at the hosting company seemed to think that it was possible, I just needed to find out here.)
If the site was to take off in the way that I imagine, I would have to spread the load over several servers soon, anyway. For this reason, it would be a good idea for me to get a head start now rather than later.