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Hi Jeff, did you realise that there are loads of these already? I’m assuming you are thinking of all businesses, not just designers? (Your website suggests a design interest.)
As my specialty is design, I can only use that as an example: free pitching is condemned by professional design organisations around the world.
All designers who belong to professional associations such as AGDA (Australian Graphic Design Association), IA Illustrators Australia, Design Institute and the American Graphic Artists Guild – are asked not to work on spec nor bidding/pitching. A good article about this is here
http://www.design.org.au/content.cfm?id=245
So, to answer your question – there are a number of those type of websites already.