You seem to be making the claim that Groklaw is somehow worthy of scrutiny (which implies that they are somehow dangerous, or at least influential, but I'll get to that in a moment). You're also implying that Groklaw does not have a competitor.
In general, you're right that demanding transparency from politically influential organizations shouldn't require a burden of proof. However, I've seen no evidence that Groklaw is either politically influential or influential in matters of law. The principals behind Groklaw may be influential in their own professional rights, but Groklaw itself is not: Groklaw does not have a horse in this race. Do you think that the judge is reading Groklaw and thinking, "Hmm, good point"? Or that the attorneys for either side are doing the same? Or that the jurors are, which is strictly forbidden? I seriously doubt that Groklaw's analyses are having any impact on the case.
You're also wrong that Groklaw doesn't have a competitor, at least where this case is concerned. Groklaw has been publicly at odds with Ars Technica's Joe Mullin, even (in at least one instance that I remember) poking a little fun at him for getting the outcome of this case so wrong.
And, just last year, Groklaw came quite close to voluntarily shutting down (http://www.linux-magazine.com/Online/Blogs/Off-the-Beat-Bruc...) entirely because the SCO vs. Linux (et al) cases, which Groklaw was created to discuss, were pretty much all settled. Any suspicions of nefarious purposes on Groklaw's part would have to explain why Groklaw was so willing to just shut down at that point.
I don't disagree that it would be nice if there were more sites doing in-depth legal analyses of technical cases targeted for a layman audience. But, the demand for that is pretty small, and so is the supply: I expect that there aren't very many legal professionals that are at the top of the game at law and technology, and possess the ability and desire to publish in-depth analyses of cases where they aren't making any money.
So now the ball's in your court. Why, specifically, should we be questioning Groklaw's motives?