I keep MongoDB, CouchDB, Sesame, PostgreSQL+PostGIS, etc. "always on" for my personal and research projects - keeping my stuff separate and using customer's VPSs or EC2 instances, etc. for their work.
Would I want to have all of this stuff running all the time on my laptop? I don't think so.
I used to keep at least one server running on our home network but now I mostly use a really cheap VPS, and a small "3 year pay in advance" EC2 instance. Running a server or two in my house is something that I only do for special needs.
Anyway, I live with the network latency hit for the convenience of (usually) not having to run servers in my home.