It would be nice to have some numbers / a scale on the map to interpret what red means. Seattle has twice as much crime reported as Boston, yet Boston looks redder.
You actually have a pretty good point, I'll have to think about this to find a nice way to fix that. I'm sure you are not the only one to feel this way.
The open data is coming from the cities that are open sourcing it. For now it's very limited I found. UK on the flip side was pretty impressive, the government is providing a feed for the whole country all in one place.