A custom cam might better be described as a "personal" cam. No way would I install anyone's secret cam. If I don't know the specs, it ain't goin in. I see some cams used by folks that I think are pretty dumb. Does that make them wrong? Hell no. Wrong for me may be perfect for you. It's all about the combo and what you're wanting the cam to help accomplish.
Cams are one big compromise. You get a little here and give up a little there. The neat thing about f/I is that you don't need a cam that causes your rig to be ill mannered. You can have it all. Great manners and stupid big power. Of course, if an ill mannered cam cranks your tractor, I'm not going to tell you your cam choice is wrong. Just becuz I wouldn't do it doesn't mean there's anything wrong with it. I've had my black car, my convertible, and my stupid big cam. I won't be revisiting any of those again.