A point can be raised regarding whether the commerical item in question is something new to the marketplace or not. Another point can be raised as to *how* the item is advertised:
"I have a new thing. Go to my website."
"I have a new thing dealing with the Lockheed/Boeing Hypersonic Transatmospheric VTOL Stealthy Submersible Nuclear Powered Bomber freom 1962. Here's some pictures, and go to my website."
In Option A, nothing would be presented that would, on its own, be of interest or value to the forum. Just uninformitive words and a mystery link. In Option B, more info and pictures would be directly posted on the forum than is often the case with *most* posts to the forum, likely including most topic-starting posts (which are often "Anybody know anything about X?").
So something I'd suggest is that ads should be permitted in the relevant topiuc forum provided that the ad-post provides actual information on the topic... and that the ad be truly relevant, and not swamping the forum. Say, a limit of one "ad" per day/week/month/whatever.
Take my ideas for what they're worth given who they're coming from. Oh, and by the way, swing by my website and buy my stuff...