First of all, I have to thank LOGODESIGNLOVE for the post regarding this significant issue.

I could not in good faith recommend purchasing a logo from istockphoto.com when they actually start offering them. They are leaving it to the designer to ensure that they are not infringing on any copyright or trademark.

And quite frankly I cannot envision the designer taking the time to do the research. It’s a lot of work. And the payment to the designer would never be sufficient in the event they were sued for infringement.

References:
LOGODESIGNLOVE
iStockphoto Forum