Stock symbols are used globally to identify publicly traded companies that offer their shares on a stock exchange. Depending on the stock exchange in question, these symbols are typically limited to three or four characters. Thanks to the brevity of stock symbols, their associated domain names are often valuable as domains in their own right.
Some companies have gone to great lengths to secure their matching stock symbol. One example that immediately comes to mind is that of Facebook,...Domain Data: 66% of Companies Don't Own Their Stock Ticker Symbol as a .COM Domain