I think you're right that the IJ at Disneyland is frequently pulled for maintenance (sometimes people leave a comment on it saying, "currently out for maintenance," rather than removing it from the map). I also think that sometimes people simply can't find it, and so they think it's gone. It's not in the arcade, after all - but rather, it's in Adventureland. So, people check the arcade, don't see it, and then remove it.
Regarding spam, I personally only notice it in LA and Portland because those are the maps that I administer. I don't have my finger on the pulse of the 71 other maps (that's why we have other admins!). I wouldn't be surprised if there are other instances of spam on other maps. But, overall, it's super rare compared with legit updates.
User system status: it's all set for the website (though not deployed yet), and we're working on the android app right now.