Michael - I worked on a project where the nephew could code circles around me, built beautiful sites, and had some pretty big clients in town.
The first time he “helped” I put his 100% validated code into 8 different browsers and sent screen shots to the site owner. Then, in a carefully worded email, asked if it was more important for the site to be written in cutting edge code, or for it to work for as many people as possible.
The nephew couldn’t get his code (and it was beautiful too, text-book beautiful) work in all the browsers at the same time for this site, and we had let the site owner know that we were not about to debug someone else’s code.
After about a 6 week delay in the project waiting for some 100% valid code that would work across all browsers, we were given permission to do the unthinkable, and the site was launched a week or two later.
While the nephew is a red-flag, most of the time the nephew is out of the scene pretty quickly once the client experiences the difference between the nephew’s customer service and ours.
Probably the most interesting part for me, was that the nephew, is now the webmaster, and we get along pretty well.