I actually think the format suggested here is wrong. Here's a sample of the MLA version:
Daly, Jimmy (jimmy_daly). "72% of college students own a smartphone: http://t.co/yyZbgVBK00 #highered". 31 Jan 2014, 17:01 UTC. Tweet
I think it should say "Twitter.com" and not "Tweet". Twitter.com is the source. 'Tweet' is a nickname. A person could use identi.ca (which uses pump.io), which would use the same sort of reference, but you would neither call it a 'Tweet' or "Identi' (or whatever). Additionally, each tweet has a unique URL. The Daly tweet cited above can be found at https://twitter.com/jimmy_daly/status/429298436736028674 - but you'll never find it without the actual URL. Not without months or years of endless scrolling.
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