'My Topics' only gives you threads that 'you' started. Not ones that you added to. For the most part it's useless, I see no reason to drop the 'My Active' function. Non-Paying members well certainly loose track of posts they have added to without it. To save on server resources would it not be possible to limit a 'My Active' to a 24 hour basis for non-payers? Oh, and before all you 'join the club and pay the 20 dollar guys' jump in, I certainly intend to pony up the bucks for my membership. I use the site often enough to warrant contributing.
Though, I've not used the 'search' function much, and my spelling could use checking... :), I think 'My Active' is essential for all users, paying and non. And to lower server resources, why didn't 'Active Topics' get removed from non-payers as well? Seems to me, that would waste server resources nearly as much as 'My Active'.