I am going to give my thoughts on this and you can take it for whatever it is worth...
I see the good and bad to this...first we will go over the good for the buyer.
Usually this type of thing is put into place to protect the buyer of the wares. It is to show that the seller actually has the product in hand. You have to understand how much fake sales there are across the net (Ebay anyone?)
It is also a good thing to star placing trust in sellers and members in good standing. Now i know you've all said Buyer beware and well you know who you can trust but sometimes you just dont. I Moderate quite a few Electronics (PC related) forums that have Market Places in them that members can buy and sell wares.
I have run across all kinds of people over the years and I can tell you that i have had a handful of high post count members that have fallen on their luck and have made some sales on trust of their long time standing and the sales fell thru only to have the buyer paying teh seller and nothing got shipped. How does the Image apply here...well it really doesnt and it sucks to get taken. I have myself once or twice over the years.
Now on the other hand it isnt that much of a bother to take a photo of the product with a piece of paper with your forum name and the actual date and include that wil the sale add...many forums do it and it's part of the rules. The really only ones that gripe are the ones who dont read the rules and just apply an add and get called out.
It does tend to help members feel more comfortable in their buying of your stuff and really if you think about it dont you want buyers to feel more comfortable so that your stuff sells quicker.
I know if some one used a hosted image for a product I just wouldnt buy from them and I dont even want to hear the no camera thing...you can buy them for 2.00 and almost every cell phone in the world has one these days... thats not the issue..
I think the issue is is that the seller just doesnt want to be "inconvenienced" by going the extra distance to sell something they wish to part with... you call it extra work I call it being lazy...I have been a Mod many years and its been something required at many forums...
Now I will say you can design limits to it... members under so many post count wishing to sell or members with few transactions must be required to add the paper to the picture... you ARE building trust here... and it IS a BIG issue.
3rd party services are a mandatory part of the market place just like Ebay's Feedback system you have and acquire Heatware from a place like heatware.com
I have had mine along time and each person gets "heat" pos, neut or Neg depending how the sale went... others get to look at it before actually doing the transaction...like feedback and can add to it after the sale has been finished. I see Heatware as a good thing and I use it religiously...
I will not vote Yes or No just because I see both sides and I DO require members of the other forums to have this upon request... members under a certain post count or little trade tranactions MUST have it...it is not much to ask... if its already boxed to ship so what its only time and tape.
I do it on all transactions where the dollar amount exceeds a certain amount... when you ship products over 100.00 and up you really want to know the person actually has it...those that are honest dont have a problem adding the paper with forum name and date...
and even though forums say they are responsible they can help... I can tell you I have had the local police show up at a few sellers homes and a few times people have been jailed for taking advantage of members... you get the good and the bad....
and just for you to see heatware.....
http://www.heatware.com/eval.php?id=49760
Now I will say that most of the forums i Mod at I am in charge of the market place...and i havent really had much issue with the current requirements and we tend to have many transactions going...people are always buying/selling/trading PC parts. i do it myself..
Trusted sellers arent required to have the paper and first time traders are and some places I have also Upon Request.... if they dont like it I usually delete their threads and they are banned from trading... i run the ship tighter than need be but I feel its my job to help protect both parties...but in the end its still up to them to make the deal or not...