Twitter is the free speech social network, officially. You can tweet whatever you want, basically, unless it's spam. But if you want to see a tweet get blocked by Twitter, try posting this:
Actually, try any two-word "get" phrase: get better, get lost, get away, get inside, get out, get asdfgjkdjghlsldskf. As soon as you hit "Tweet" the text will disappear, never to be seen in your timeline or elsewhere.
Some guys at StackExchange floated a fun conspiracy theory before landing at the truth: This isn't censorship or or an easter egg. It's a little artifact from Twitter's past as an SMS service.
If you wanted to, you could still use Twitter solely through its SMS interface using text commands. Here are a few more:
See that, right there in the middle? That's why Twitter eats your "get" tweets.
A majority of these commands aren't things you'd otherwise use in a two-word tweet, and most only work through the SMS service — you can tweet "suggest something" just fine from a computer or app, for example. A couple years ago you could even type "accept [username]" and force anyone to follow you, a command that, like "get," had been lying mostly dormant for years.
Anyway, whatever the reason — probably oversight, or just "who cares" — the "get" command lives on.