Spaw's got it. That's the core of it. Of course several other details could be added to demonstrate why this case is of particular interest.

Yes, the process of "trying the case" in the press/internet is problematic, given the way the evidence trickles out and is liable to the biases of those who present it (to say nothing of the biases of those who hear it).

It's clear (at least one hopes!) that there is relevant evidence that is not currently public.

However,

It's the contrast between the two cases Spaw outlines that causes (some) people to be paying such close attention: the bottom line question is whether the evidence and the process are being handled fairly and appropriately. Conflicts among statements made by those in the process (the police chief, and others) cause this question. And, in the history of American jurisprudence there are historical precedents of miscarriage of justice as a result of bias against African Americans. It behooves us to watch closely and keep pressure on the side of justice.

Questions...

Justice for Trayvon Martin: Questions (Jonathan Capeheart, Washington Post)

The killing of Trayvon Martin: More questions (Jonathan Capeheart, Washington Post)

Trayvon Martin: The 5 Key Unanswered Questions (ThinkProgress)

~ Becky in Tucson