Now, for slashdot, the slashdot crowd definitely has some responsibility. Still, they did pretty much anything they could to antagonize them (although, I'm not sure what they could have done not to, it seems like it's a pretty important part of being a slashdotter to hate on the staff).
I wouldn't go that far. I was on Slashdot for a very long time and witnessed many changes of ownership. Sure, there are always a few people that will grumble when anything is changed, but I don't think any of the ownership changes caused that much uproar before Dice came along. Auto-playing video ads of models walking down runways on Slashdot? Adware/malware bundling on SourceForge? Dice made it really clear that they didn't have an ounce of respect for the community. I think the bulk of the community would have tolerated reasonable efforts at monetization, but Dice went way beyond reasonable.