The 140 character limit on Twitter may be a constraint for some, but it lets others go retro.
On February 20, an antique Commodore VIC-20 (circa 1981) at the Personal Computer Museum in Brantford, Ontario was used to send a tweet. There was a CBC report on YouTube the day before, and the event itself was recorded for posterity here.
The program had to be loaded into memory from a cassette tape. Talk about constraints!