True, every new edition has caused some folks to get all cranky. But it seems now that we live in the future, with this new-fangled internet, the wailing and gnashing is louder and more widespread. Perhaps that's just perception, as the cranky folks now have a venue to vent their spleen upon.
Well, while the internet makes it easier for people to gripe, I'd not say that this griping is new. I've heard lots of stories about grognards during the AD&D 1e/2e transition being just as bad, for example. At least with 2e there was a lot of backwards compatibility (thus 1e players could buy new 2e adventures and even some supplements and use them with often little adaptation), unlike 4e which seems to be specifically designed to have no backwards compatibility (which forces the issue of the schism).
Personally, I think that the 3.5/4e split is particularly loud because of several reasons.
1. There was not a broad consensus in the fanbase that 3.5 needed overhaul or replacement (I believe that the reason that 3e was so broadly accepted and there are few 2e grognards is that there was such a general consensus). Some people wanted something new (be it OD&D, C&C, 4e, or who knows, but 3.5 wasn't satisfying them), some people would buy anything that WotC made, but there were a lot of people who were quite happy with 3.5 and didn't see a need for a new edition.
2. The game changed so radically in presumed style, terminology, mechanics, and "flavor" elements such as setting presumptions like cosmology that it resembles D&D in-name-only to some fans.
3. WotC bungled the marketing so badly that it should be used as a textbook way not to sell things: their idea of spreading what used to be core throughout more books in what was seen as a blatant attempt to pressure gamers to buy more books, and the initial "3e is wrongbadfun" marketing didn't help either as it turned lots of potential buyers who were happy with the current product away. Seriously, what marketing guru would tell you to market your new product by openly insulting your old product that you are still selling and has been a smash hit? Do they advertise a new video game sequel by saying that the previous one wasn't any fun and was boring and if you played it you weren't having fun, so buy this new one instead so you'll have fun because it's totally unlike its predecessor?
I haven't seen quite as much rancor over the WoD/nWoD split, but I've seen it somewhat. At least with nWoD there were some very needed and innovative design ideas in the main "splats" (Vampires not being inherently tied to generation, for example) and improvements in marketing (a single core book for the entire line, for creating humans). I've seen actually several GMs run games using the nWoD rules (somewhat adapted) for games set in the original WoD setting (they prefer the new rules, but most of the old setting). I've seen more people adhering to oWoD Larping than tabletop, but that's just my experience.