First things first, I am only writing this out of curiosity and I don't want to come across as arrogant or anything.
I also wanted to say that I have sold many phones over here for profit, but as JMP said above I always try to price the products at very genuine prices. Some members have, in the past few weeks, bought stuff from me without me creating a sale thread or in JMP's case without even seeing a photograph. For me the decorum of the forum is very important and that is why I have decided not to sell any stuff over here unless it is genuinely something personal. Having said that I do feel, from the responses I have got recently, that some members don't mind paying a little extra to a trusted member so that they don't get involved in the hassles of importing,etc and get the product within 3 days instead of the week long wait that usually accompanies such purchases and I don't mind losing a few quid from my profit because I genuinely feel a sense of brotherhood and camaraderie with my TE mates.
I understand that from your perspective that you want the forum to be more about content and discussions than the marketplace. From my own experience I can tell you with surety that the Marketplace and the presently lacklustre Dealer section are actually big crowd-pullers and the people who are genuinely interested in the discussions stick around, like I did.
I am not asking you to even consider changing the rule as that was not the reason behind my rant. I just wanted to share my 2 cents.