There were joemoneys in the BBS days just as surely as there were NorthWesterners.
I'll concede, though, that the shallow end of the gene pool is more strongly represented nowadays on message boards than it was earlier on BBSes. It's all because of the cost of admission. Not only monetarily but in smarts. The internet used to be the sole domain of intellectuals ("The Good Ol' Days") because you had to be a hard-core geek, and a connected one at that, to be there.
BBSes were more accessible to more people, but you still had to be able to figure out how to use a program like Procomm (a favorite tagline of mine is: "BitStream changed my life -- I used it to download Procomm.") and usually had to dink around with your modem and interrupts (or at least be able to tell Procomm what brand of modem you had, its com port, and IRQ), and figure out how to add to your dialing directory, choose terminal emulation type, etc. And you had to have the wherewithal to get a computer to begin with. And install software from a DOS prompt. A bit of a barrier to entry, but a low enough one that the average online IQ and capacity for civil discourse dropped.
Then along comes the WWW, cheap computers, online access without computers, browsers built into the OS, a point-and-click OS, and suddenly there's no barrier at all. Of course, it's easy to predict what I think that did to the average capacity for civil discourse.
On the bright side, our online communities also became increasingly populated with the best and the brightest; who only weren't on before because computers not only were low on their list of priorities, the people were so specialized in their knowledge that they didn't have the geek level knowledge of computers necessary. Sadly, they're outnumbered by the folks at the other end of the spectrum. The deep end of the pool got a bunch bigger, but the surface area of the shallow end is now about the size of the Pacific. Fortunately we have (IMO) on this site, a more desirable mix. A goodly number of the smart folks, but nowhere near the percentage of knuckle-draggers that RB and Yahoo are so well-known for. A mix similar to that seen in the BBS days. Or at least on my board.
So we started out with bright geeks. Then we opened the doors enough to admit people who might not have been quite as hard-core as far as geeks go, but were geeks nonetheless. Then we tore the doors off the hinges and were joined not only by all types of intelligentsia, but also every knuckle-dragger who could hunt and peck on a keyboard.
Or, to look at the same phenomenom from another point of view, as I tell my wife "98% of the internet is crap, but the other 2% makes it worth it." Since the bursting of the bubble, I'd call it more like 95/5.