There are about 10 million public geotagged tweets every day, which is about 120 per second, up from about 3 million a day when I first started watching. The accumulated history adds up to nearly three terabytes of compressed JSON and is growing by four gigabytes a day. And here is what those 6,341,973,478 tweets look like on a map, at any scale you want.

Read more here:
https://www.mapbox.com/blog/twitter-map-every-tweet//