It's most likely because "get [username]" is the Twitter SMS command to retrieve a list of tweets from [username]: https://support.twitter.com/articles/14020# I would wager a guess that you can't tweet "Fav Better" or "Stats Better" either.
That being said perhaps people should use g3t better :-).
It is an interesting case study on overloading a channel (in-band administration vs out-of-band) and damaging legitimate traffic. A fix would be to prefix the command keys with an introducer :get <username> or :fav <user> but given the bazillion clients and such doing that would be hard.
Most famous in-band admin hack has to be the +++ syntax for Hayes modems which flipped the mode bit into 'command' mode serial comms mode. It was even patented.
Unlike this case the +++ hack did not really limit legitimate data you could send on Hayes. As far as I remember it had to be preceded and followed by pauses, so transmitting this comment wouldn't trigger it.
I'd love confirmation or denial of that patent thing.
"Hayes had patented this concept in 1985 in patent #4,549,302, the Modem With Improved Escape Sequence With Guard Time Mechanism, generally referred to as the "Hayes '302 patent". Hayes licensed the guard time to other manufacturers for $1 a modem – a charge which competitors derisively termed the "modem tax". A number of manufacturers banded together and introduced the Time Independent Escape Sequence, or TIES, but it was not as robust as Heatherington's system and never became very successful."
get bend
get cake and meet me
get lucky:
get me some abc
get this: These were ones that came to mind in 2 minutes.
get it?
edit: These lines give my comment a weird tone. Not intended, I just thought of random common examples.
I agree with treetrouble, however, this was a really bad engineering decision. They should have come up with a tweet prefix to mean "command", some symbol that would not ever start a real tweet.
Just as an example let's say "q", followed by a space, followed by the command with the appropriate number of parameters, e.g., "q get username". That would allow otherwise-reasonable tweets that are currently being mis-interpreted ("get better" vs. "q get better").
That's just an example. There are other ways around the problem too without making things too inconvenient on a smartphone user. And sure it's possible someone somewhere will want to write a real tweet that says "q get better", but that's far far less likely than someone somewhere wanting to tweet "get better". And the point is that allowing a non-trivial portion of the tweet-space overlap with the command-space is a bad decision. A trivial overlap (like "q get better") would have been a much better decision.
It really is poor engineering, any non-letter prefix would have been good enough.
I can just imagine promotional tweets gone wrong, e.g.:
"Get your tickets to Blind Guardian concert! Only 500 left!"
If you see an imperative "get" with an apparent subject, it's probably a topic rather than a subject:
"Paul, get your boots on and get going!"
You are speaking to Paul:
"Get your boots on and get going!"
You use the topic to designate or call attention; it's not the subject of the sentence.
get directions
get him to the greek
get glue
get smart
get low lyrics
get off my internets
get rich slowly
get away today
get to know you questions
get fuzzy
When I saw that I thought, "Wait, there's actually a manual for this thing?". Of course there is, but I wonder how many people have actually read it. <1%?