You'd be surprised how trusting people are, I'm explicit that nothing of great personal value or import should ever be stored unencrypted on these since at the end of the day I hold the keys to the proverbial castle. Quite a few of my customers are people I know from BBSs I used to and still do frequent. One even hosts a few BBS servers.
On the whole, I could probably net in the 11-15K range per month if I expanded but that requires a lot more work and I'm not sure the money justifies it. At the moment its a (usually) enjoyable hobby that helps me keep current in sysadm-land and make some money at the same time
(Though I realize you're doing more than that if you're renting out physical boxes too.)