I suspect it's the same in a lot of trades, e.g. hairdressers, builders etc. If someone is keen, capable and competent, their ultimate goal could be to run their own business. So in effect, you are teaching them how to do that, in return for helping you do the same thing. If you view it as 'teaching someone how to put you out of business', then you have a problem, and judging by some of the posts, a very real problem. I know of a hairdresser who lost a member of staff. On her last day, she copied the client database to a cd and proceeded to work through it from home. So I can see why business owners are very wary when it comes to employing staff and it should also explain to people looking for positions why this is so.