I don't think it's anything that organized.. I think it's just all the major roads in the immediate area and they are fishing for whatever.
If you google earth, or street view, you'll find that all that is up there is farm land, or farm land that's been converted to huge housing developments in the past few years (well 15 or so, I am getting old). There are no services to sepak of until you go on the south side of Hwy 26, into Beaverton etc.
When we first moved to PDX in, er, 81.. my sister's b/f lived at 185th and our house way off the Sylvan exit of Hwy 26. I would drive him home occasionally, it it seemed like *forever* to get out there.. like really out in the boonies.
Same for the Beaverton side of 185th; I'd take my sis there for swim practice and the pool complex was literally in an orchard, in "the country".
I think that the roads are basically ALL of the main roads that have any probability of having video installed. Everything else is just residential.
I know this will get missed but I'm going to stick it in here anyway. The reason the wandering off theory bugs me so much is confirmed by looking at the school in google earth. There is a farm immediately behind the school, and then forest. The school is geographically cut off.. there is nowhere reasonable for a 7 y/o to 'wander' off to.
And yet, I don't like the 'snatched from the parking lot' either. More and more and more it's got to be someone he knew, and he left willingly?