SUP will not work for Twitter or any other service that deals with very large data sets.
In essence, a Twitter SUP feed would be one JSON array of all the Twitter users who have posted a status update in the past 60 seconds. a) The SUP feed will consistently contain a few million array entries. b) To build that feed you must do a select against the tweets table, which contains a few billion records, and extract all the user ids with a tweet that has a published time greater than now() - 60. Good luck asking any DB to do that kind of select once every 60 seconds. Dewald