What the guy could do if he wasnt happy using their server, would be to ensure that they exported a backup of the site daily to some shared server of his own choice somewhere that cost little, so that if they did go down, he would still have his site.

In my experience, there are some sites that you do need full control of the server for some settings and a dedicated server is only way to have that control. So they could be straight up about that, as they would unlikely get a separate dedicated for his business, due to the cost being into $100s.

If the needs he has specified require certain server settings, that could be the reason, it would be true especially if there is alot of database activity as they would want allocate resources specifically, but like you say, risky if anything happened to them, which is why I would suggest he ensured an exported backup daily to an alternate server of his choice that wouldnt matter about the settings, just to hold the files.

__________________
Hairstyles - Pictures of 2008 hairstyles and a virtual hairstyler demo.
Price Comparison Site - Compare prices of well known brands and products.