Oh damn you, Windows! I was working on your second question as my PC decided to update for the month. So, I'm starting over here...
I took it upon myself to have business cards made up to place on parked vehicles or give to Jeep people I meet in public. I feel its a more tangible method for attracting new membership. By giving them something to touch, it's harder to forget than something they heard.
At this time,

does not advertise aside from sponsorship. I think the cards are a cheap form of advertisement. Though I find extreme benefits in recruiting people you meet in a restaurant, parking lot or on the trail. Chances are good that you had a moment to talk to them and get a feeling of the type of person they are. Advertising will attract anyone who sees the advertisements towards our site regardless of their personality type. A couple minutes of talking may get you to realize that a person isn't quite right for the group, or vice versa. I am all for a larger membership, but I've always preferred quality over quantity.
Example: I looked at joining a local club a couple years ago. I went to one of their meetings (which I thought the fact that they got together once a month to talk business and BS was awesome (easy to do since they're all local)) and quickly realized that they just weren't the type of club for me. They're a great group of guys, but their priorities were more towards show and shines than mud. My pile isn't worth putting in a show. Most of ours aren't.
Why would anyone need an AR15...? The AR is a reliable, low maintenance, ergonomic, accurate, effective and versatile rifle. It's multi-caliber parts make it an excellent candidate for hunting, target shooting, home defense, plinking or apocalypse prepping. Accessories come in all different shapes, sizes and colors making them highly customizable and changeable for different people. Magazines come in different capacities to suit your needs if you're legally allowed to.
I think the real question is: Why not own an AR15 or variant?