The Modern Language Association (MLA) has recently formalized how to cite a tweet (a post in Twitter), should one need to do so.
In many cases, no. No one needs to quote and provide citation for some illiterate youth ranting about whatever pop singer or whatever's awesome or lame on Saturday Night Live. Yet there are thousands and thousands of scientists, journalists, politicians, celebrities, and figures of authority on Twitter and many of them do deliver a quote-worthy payload. If you're writing a formal paper of any stripe and need to cite your source when quoting them, it should look like this:
- Christian Fredrickson (sxoidmal). "This is how to cite a tweet." 5 Mar 2012, 1:32 PM. Tweet.
An example of an older tweet, from a twit:
- Sierra Kusterbeck (SierraVE). "Advice from Sierra- always skip the first 3 days of school. Scheduling is definetly [sic] a mess & they'll never even notice." 24 Aug 2010. Tweet.
Note the date is not indicated in this post, no date more specific than year, anyway. I had to go through my own photo archives to find this image file's date from my screen capture, and I had to trust I'd taken it on the same day this post went out. In cases like this, the MLA suggests Twitter citations are not meant to be an accurate register of when things went live online but "approximate guides".