The one thing that I'm finding most bizarre in all the details of this case is the quote from the step-grandmother in this article
http://www.oregonlive.com/portland/index.ssf/2010/06/details_emerge_about_the_day_k.html (link already posted many times): It will be difficult to give him the news, Moulton said (referring to Kyron's 16 year old stepbrother who lives with her, and was away on a Boy Scout camping trip with his father for the weekend).
Hellloooooo! FBI specialists are being flown in from all around the country, the local sheriff's department is working this case 24/7, and no one has contacted the stepbrother? Where's this camping trip? Antarctica? There's absolutely no way any Boy Scout group is going anywhere for a weekend, that they couldn't be reached pretty easily. Possibly out of cell phone range, but if so, then almost certainly one of the leaders is carrying a satellite phone in case of life-threatening emergency. And if agents can be flown across the country to get on the case, obviously somebody can hop in a helicopter and go pay a visit to this Boy Scout group if there's really no phone contact at all.
It seems very likely that Kyron and his older stepbrother spend at least some time together, and the stepbrother should have been on the very short list of people interviewed *immediately* to find out if Kyron had said anything to anybody that might provide a clue. Maybe something that sounded like idle fantasy at the time, but now that he's disappeared would sound potentially like a real plan or experience.
It strikes me as so incredibly unlikely that investigators haven't already spoken to the stepbrother, that I'm thinking maybe they have, and just haven't shared that fact with the stepgrandmother (and maybe not with Kyron's father, stepmother, or mother, either). Which makes me wonder if the stepgrandmother is on the suspect list. She might not be happy that her daughter is so involved in raising her stepchild Kyron, but is less involved in raising her own son, who is currently living with his grandparents.
Also, along the lines that Dragonfly1971 has mentioned in a couple of posts, as far as I've seen there's been no confirmation that anyone actually saw the stepmother leaving the school, much less saw her leaving the school *alone*. That's odd. Because with all the extra people who were around that morning, including other parents who'd come in for the early morning science fair set-up and would have been leaving around the same time. It may be that investigators already have this information from witnesses to her departure and are withholding it for some reason. But it's a gaping hole in the fairly detailed story we've heard so far -- just like the gaping hole (at least according to the stepgrandmohter) of the 16 year old stepbrother not having been questioned yet.