how to collect millions of tweets?

I was bro开发者_运维百科wsing through fflick, nicely made app on top of twitter. How do they

1. collect millions of tweets?
2. accurately (mostly) categorize tweets into postive or negative sentiments?

1. The collect millions of tweets probably by crawler twitter with their API. Probably searching with Streaming API for keywords related to films, or just searching their own timeline looking for what their followers have to say about films.
2. Don't know. Probably using some natural language processing techniques from good old AI textbooks. :-)

2) look for smileys - ;), :), :D, :(

A few places provide the latter vas a service now. Check out ViralHeat and Evri:

http://www.viralheat.com/home/features http://www.readwriteweb.com/archives/sentiment_analysis_is_ramping_up_in_2009.php