I don't understand how posting on the TDHA site will increase membership.

For the most part, the only people who visit the TDHA forum are already members. Isn't it the non-members that TDHA is trying to attract?
My opinion is that the TDHA forum is "cluttered" Heck, the first forum has 8 stickys, the second forum has 10 redirects, out of 20 topics. That said, it's much better than it has been in years past. You see many of the same stories posted on TB, Jagdhunt, TxOutdoors, ETHD, TDHA, As it is, ETHD has the most hog dogging traffic AND a board setup specifically for TDHA, I would argue that alone gets TDHA as much "advertising" as any other method currently employed.
With that said, I am all for TDHA trying to gain membership, as I believe in strength in numbers. It's my opinion that there needs to be an effort to attract bird doggers, coon hunters, duck hunters, etc...Hog dogging is just a small percentage of what the TDHA is about...it's time for TDHA to support some of the other venues, and in return, they will gain membership through the newly aware hunters at those venues. Same way the numbers have grown to what they are currently, TDHA has supported hog dogging, and hog dogging has supported TDHA. Diversification WILL attract new members.
My .02