Honestly, I would think that would be in Fair Use or some other acceptable exception - and in the long run, not worth persuing one way or the other - some copywrite holded may disagree and that's why the couts exist.  Usually, in terms of comics, i've only heard of legal action coming from use on covers or in advertizing - such as the Dr. Strange/Amy Grant situation from a few years ago. 

Often when drawing something technical like a car, or a building, it is hard to say you used THIS photo or that photo since the Object or Building IS what it is, and many photos can likely have been taken, unless there is some unique composition you've copied.   When you go into Models or Actors, however, it's easier to see "Oh, look, that's Kevin Costner from the Robin Hood Poster in the Ultimates this month" --

Okay, that, I find kinda lame.

Looks like we've been discussing two separate things here. I'm saying, I think it's okay if JB traced photos when he did his Trek pieces for Star Trek Who's Who, to get the likenesses right. I don't think it's wrong if somebody traced David Duchovny's photo for a cover of X-Files. I have no problem with someone tracing a photo of a Ford Mustang, or a tractor trailer, or a locomotive, or the Empire State Building, if it made their job easier, and the piece more accurate. I think this is what Neal and JB were talking about when they said photos were tools. I don't think that kind of tracing is wrong or unethical, or cheesy.