where do people place their multi user meta store? I'm going to use mysql but I don't know were I should stick it. on the name node or on its own server?
Hadoop can really trash the page buffers on a datanode so you probably will do well to keep mySQL off of any of them.
The recommendation to run Hive outside the cluster is a very good one, if only because you will have serious balance problems if you run it inside the cluster.
It can be on any machine really.
We installed hive on a node that is not a cluster member (but is only used for staging data to load into hive) and setup the metastore mysql instance there.