Perhaps with a more civil outlook on things I can venture another opinion on enhancing the site per the OP's wishes and also drawing more members.
Ads? Well, I come here mostly for the articals and forums. Ad's are what drives me away from sites.
Perhaps the biggest factor contributing to the lack of membership is the economy. Everyone, generally speaking, has less disposable income. UL people are kinda out at the fringes of the camping community, soo, one of the first things that can get dropped is costs ascociated with it. People still go camping, after all, it is a low cost activity, generally. As an example only, "I do not need a 8oz Cuben tarp when a 14oz Silnylon tarp is still usable" is the attitude. Of course you get a range of people that can and do still buy new gear, just not as much as they used to. Same for membership. I would not have a membership, except I was undecided to reup, despite the value of the site's stuff. My wife said go for it as a Christmas present. This is a good idea and is well presented on the front page.
There are fewer people interested in hiking. Less population interest means less people at the fringes. Unfortunatly, more people are simply NOT in my woods., though some areas remain about the same or even increased in popularity. NY state parks are a good example of those more heavily used. Trails are less heavily used. As are deep woods canoe trails and longer distance trails. People like to hike for a day, it simply isn't in their interest to hike for a week. Perhaps the articals should diversify in content to fit the newer audience? Hence providing more value to these types of more mainstream hikers?
You mentioned charging to use Gear Swap. This was discussed and found to be an expensive option to implement. It may well be a truely viable alternative. Again, because of the fringe nature of light weight hiking(one of my hiking buddies still thinks I am a bit wonky,) Charging for sales might indeed be an option. But, I suggest a simple aproach to minimize any programming/implementation costs. Perhaps a simple charge per ad (up to 3 items) form rather than the forum like posting that currently exists. Questions to the poster, via PM, all exchanges to the poster. And, an automated removal of the Gear Swap ad after a few days. Cost, is required as is condition and general description, including weight. A sugestion only. Perhaps we can entice more non-members to the site, and, decide if they want to join. Maybe not... 3-4000 is a lot of money in programming and could well go into forum upgrades. Unless somebody wanted to do it for no charge as a test solution.
I suggest that more questions be posed. Often, it is difficult to write about "things." Determining a main subject, organizing a plot line, performing tests, evaluating gear, conclusions, and opinions. There is a HUGE body of knowledge out here. Asking a single very specific question, then publishing the best answers chosen by a group of staff, lifers, members and/or non-members chosen for some demonstrated expertise related to that question. Again, Content->readers and Readers->members. This is a Magazine, after all.
Anyway, my thoughts only . . .