I knew a little php before I got into the phpBB stuff, but I also didn't know about mods (or were there really no mods for 1.x? I can't remember, that was so last century

) and in late 2001 I found myself jobless like so many other techies, and went out on a limb doing system administration and freelance php coding, and landed a gig customizing phpBB systems. Found my way into just about every nook and cranny of the codebase over the years, and have implemented little custom tweaks here and there on just about every phpBB I've had my hands on... only to find out later that there was already a mod that did something similar.
Spam on phpBB used to be very manual, with people searching out forums and registering and posting one-offs... that was really tough to stop, but then some smart people started making the spam bots that go nuts trying to register and spam or find guest-enabled forums or what have you. We did something similar to what you've got, without actually removing the form input field... we thought about making them all hidden on the first go when a new user is registering (but not hidden when going into profile to edit it) but decided to leave them there because people were still doing manual setups... we put in a BIG RED WARNING on the registration that says not to put anything into the location, web, IM or sig fields, and if anything is put into any of those fields, the registration aborts after submission and it fires off an email to me, so if it looks legitimate I can follow up with an email to the user to see whats up. It's available as a mod now, buried in the phpbb mods list somewhere... not as elegant as I'd prefer, but it seems to do the job well. We've only had 2-3 spams since putting it in place several months back, and we had to keep checking up for spams throughout the day prior to that.
I get probably 4-5 of those spambot registration attempt emails every day, only twice have I seen a legit user overlook the warning and get snarled up by the mod, and both times the user realized what they did wrong and got set up just fine without intervention.
We really can't afford not to let the search engines crawl the site, it's our #1 traffic generator... since I took over the site and made some mods to ensure that keywords were in the right places, search hits have gone through the roof, as have new users... Honda makes a bazillion of those little 250 motorcycles every year, and most folks who buy them would have no idea that there was a community to support them if we weren't turning up on searches... our whole site is the forum, so it's kind of a necessity there.
After tooting my horn and saying I know a lot about phpBB, I'm embarrassed to say i'd not heard of it by the name "Santy-A"... i'd heard of input handling exploits, but those were fixed starting with 2.0.12, and I had been out of the loop for a few versions after I got back to work in the tech sector in '03.
I can't stand super-active forums, especially if they really divide up the discussions into a million almost-related subfora... I already have too much to do every day, and some admins try to make it difficult to participate and/or get things so huge you just can't stay afloat, sort of like phpBB's own forums. I scan around there from time to time for mods and patches and if I'm having a problem, but I just can't be bothered to keep up with the day-to-day.
Another bike of mine is the KLR650, and I was very active on that forum when he was on phpBB until he split it into no less than 75 subfora... after which he found that it was too tough to administrate and he flipped over to vBul instead, and about 5 months after that his ISP managed to absolutely trash his database, and he didn't have any backups. He hasn't quite recovered since, but it is pared down to about 6-8 subs with an astoundingly small subscriber base compared to what it used to be. Shame, it WAS a good resource, once upon a time.
In 3D land I've got 3 motorcycles, a jeep, a truck and two cars... all to myself... 3 dogs... 2 computers (laptop & desktop)... fly about 500-1000 hours a year on flight simulator, tinker in the shop and make my wage specializing in SAN/NAS storage systems, data protection and disaster recovery plans for IT... I reckon that sums it up... and some day... a bus conversion.
Oh, and about 10 yrs ago, I was actively working towards conversion of a 1964 VW Beetle and a 1970 VW Bus to full electric traction, but a horrible divorce ended those plans. Was doing it with a lot of email help from some very talented acquaintences, some of whom you probably know... by the names of John Wayland, Bill Dube', Otmar Ebenhoech and everyone else on the EV mailing list back then.
