Has the TestNet ever been reset?
The current testnet is on its third iteration, somewhat unimaginatively titled testnet3.

It was put that way by this commit:


  Testnet, Mark III  
  
  gavinandresen authored 2012-04-12


Before that, we had testnet2: (though we didn't call it that back then)


  Reset testnet with a new genesis block  
  
  davout authored 2011-02-03


Before that, testnet:


  Gavin's TEST network as -testnet switch, misc fixes
  git-svn-id: https://bitcoin.svn.sourceforge.net/svnroot/bitcoin/trunk@168 1a98c847-1fd6-4fd8-948a-caf3550aa51b
  
  s_nakamoto authored 2010-10-19


Man, sourceforge. Brings ya back, doesn't it?

Essentially, the devs want testnet coins to be worthless for two reasons:


to make them easy to mine
because it's nice to have a place to demonstrate attacks against bitcoin without actually disrupting the network. You can show that an attack is valid without costing people real money.


Now that I think of it, we're due for a new testnet soon. Sell those testnet coins!