Well, at least with Puerto Rico, its partically because (1) It has a lot of delagates, more than Oregon IIRC, and (2) It's effectively the last contest - Montana and South Dakota follow it, but have few delegates, and I believe are expected to vote Obama. Therefore, PR gets a lot of press because it is likely to be the absolute end of the process; if Sen. Clinton cannot eclipse Obama in whatever metric you choose, then she is not likely to thereafter.
Just out of curiosity, since you brought up Puerto Rico, do you (or anyone else, really) know if PR's delegates each get their own vote or if they get half votes, as is the case in Guam and (I think) Dems Abroad?
Full vote at the convention for PR.
