Some time last year I did some work using the Twitter Stream API and ended up with a data set of a few thousand tweets. It was interesting to mine some basic data for the client and I thought it might be even more interesting to see what I could come up with if I mined an even larger set.
After writing a small script and setting up another Twitter dev key, I was able to gather about 130,000 tweets that mentioned #yolo and had geolocation data attached. MongoLab made it easy to quickly dump that data into a MongoDB store. It ran for approximately 3 months, plenty of time to think about what to do with the data.
Google Fusion Tables lets you import a set of data and visualize it on a map. My data set fell well below their limits, so I was able to put my eyeballs on the hotspots for #yolo in the past 6 months.
There are no considerations for population density or incoming geodata precision here - this is more of an exercise in data gathering and rapid visualizing before I jump into viz tools like Dygraph or D3.