Multiple MySQL schemas

Hi all.

We are wanting to create an app that contains multiple clients. Each clients has anywhere from 1 user to more than a hundred. We had the idea of separating each client into its own database schema. This reduces the single point of failure - if 1 client db dies, it doesn't kill the others. This keeps the individual schemas smaller, which will allow us to asynchronously (for lack of a better word) transfer our backups to our network w/o causing bottlenecks. It also guarantees the separation of data (even though the application takes care of this, it's *that extra step*).

Is it reasonable to create a new database per client? Or should we cluster several clients together (5-10) into a single database? What are the pros and cons of each? Note that some clients are *linked* and share data, so those would not be mutually exclusive. What is the maximum number of schemas per MySQL instance - I'm guessing this is based on the filesystem (RHEL)?

Thanks in advance,
~Philip