I've never seen the fairness of after hours trading. The majority of people don't have access to it (that I've spoken to), yet that is when you see some major moves (up or down) in a stock.
Trading outside these regular hours is not a new phenomenon but previously was limited to high net-worth investors and institutional investors like mutual funds.[2] The emergence of private trading systems, known as electronic communication networks or ECNs, has allowed individual investors to participate in after-hours trading.
The majority of investors can easily get access to after hours trading these days. A simple Scottrade account comes with the ability to trade after hours.
That's only because companies tend to release market sensitive information outside of trading hours. If you do it within trading hours, a trading halt must be in place. In which case, the major moves up or down of a stock is still outside of trading hours. Price changes are discrete, not continuous.
Congrats to Tesla for turning their first profit!