Who hasn't had some variation on the following :
Potential client : You can design the site for free, then when its making lots of money which its sure to do because my idiotic business plan cannot fail we'll definately pay you something! There might even be more work for you improving the site!
Me : Sounds interesting but I'm far too busy at the moment (thinking Oh Fuck Off!)
Also another good one :
Me : how will the site make money ?
Client : Once its getting loads of visitors we'll make loads from advertisers! mind you someone will probably buy the site off us for millions by then!