You know, you are right. It's funny, I don't remember this much handwringing on CBlog when we went through our record 18-game losing streak (I was a lurker back then). Maybe in those days everyone was so focused on looking for glimmers of hope!
It's great to cheer for a contender again, but I think people have really raised their standards. Rooting for today's Celtics beats the heck out of hoping Mark Blount, Raef LaFrentz or Ricky Davis is gonna help us win a few games moral victories.
I think most of it comes to expectations. With that '07 team, the expectations were zero (and in fact, a lot of fans were rooting for the team to lose). Therefore, there was a lot less of a divide between fans. There was obviously some venting, but not much; it's hard to get *too* emotionally invested in wins and losses when you're a bad team.
With the post-KG Celtics, though, it's different. In 2008, there wasn't a ton of venting, because the team was winning. In the Atlanta series there was some hand-wringing, but overall, fans were just excited to be contending again.
In 2009, the team played its heart out, even without KG. Again, it came down to expectations. Fans didn't have high hopes, and since the team was playing with a ton of effort, there was less to gripe about. Plus, wins and losses wise, we did very well.
Last year, though, things changed. The team started to lose, and lose often. The effort wasn't there. The Celtics started to lose games they should win, and frequently. That's where the frustration of expectations first came out very strongly. When you see a team losing for reasons outside of your control, and you feel the team *shouldn't* be losing, you vent. Unfortunately, that venting is often at the team, and it causes fans to lose hope.
This year was more of the same. At the beginning of the year, when the team was stomping opponents, the game threads were largely positive. There was a bit of hesitation while people worried about whether the team would revert back to last year's form, but all and all, neither the game threads nor the blog as a whole were unpleasant. Some of the posters that would get the label "very negative" were in fact present and cheering the team on.
Then, the trade happened. Not only was this a divisive moment, but it coincided with a downturn in winning and losing. Once again, there was a frustration of expectations, as fans saw there team which was clearly the #1 team in the East begin to drop games that it "should" be winning. A lot of fans became even more frustrated in 2010, because they believed that it was management, and not the team, that led to the results. Naturally, that leads to increased venting.
There are really only two things that are going to end the venting in the game threads, I think: either the team starts winning again, or something causes fans to lower their expectations.