Are you sure you're not a fly on my office walls?
There've been conversations, some of which have included discussion of a conversion routine to import vBulletin's database format into ours.
vBulletin is good stuff. It becomes extremely slow and clumsy when you start getting into iHub/SI-like sizes though. But since it's built for smaller operations it can include features that just aren't viable at larger sizes. Like the count of how many people are currently online. We used to have that info on our management screens and ditched it because it was so darned expensive. Currently, at any given moment during the day, there are several thousand currently-active connections. If there were hundreds, that'd be okay. Just not feasible to track thousands of users and what they're doing.
vBulletin (and its ilk, like UltimateBBS) are great turn-key solutions for hobby boards with no larger aspirations. They can't, however, run on the scale a site has to run to generate adequate revenue to provide their operators with decent enough salaries to justify doing it fulltime. Which is a real problem for people who have large aspirations but use off-the-shelf software.
If a site gets big and busy enough that it requires much faster software/hardware and full-time management, but can't have one or both, it implodes. Witness SI and RB. Same thing happened in the BBS days but in a different way. If all of your incoming lines were constantly lit up, the people who were constantly getting busy signals eventually quit trying to connect, and suddenly you're stuck with a lot of phone lines and only a few of them in use.
We were heading down this path ourselves recently. Fortunately, I lived through the same thing in the BBS days, read the writing on the walls, and upgraded hardware in time. And will soon be installing the load balancer and another webserver to stay even further ahead of the curve.
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