http://www.vgchartz.com/terms.php
part 4 under "Your Conduct on Our Site"
Without limiting the foregoing, you agree that you will not use our sites to take any of the following actions:
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4. Advertise or offer to sell any goods or services for any commercial purpose unless you have our written consent to do so;
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e-bay is generally fine, just don't spam. If you are hawking your wares for a company, then get approval from ioi.