Since AIM screen name must start with a letter, there are only 33,696 valid three-character screen names (), and 46,656 valid three-character second-level domain names per top-level domain ().
AIM screen names
Since all of these screen names were registered in the middle 1990s, mostly by America Online members, these are a form of online "rarity", sought after by youths, hackers, or anyone wanting their screen name to appear impressive. 3chars are regularly sold or traded online. Many people have cracked the password of 3char accounts through brute-force search or using AOL Exploits and hacks to obtain the accounts.
Additionally, complex methods of screen name theft have been developed over time to allow AOL crackers to gain unauthorized access to rare screen names, including 3chars. In late 2000, one AOL cracker reportedly developed software which used an AOL security glitch  to gain access to all three-character screen names vulnerable to that security issue, effectively bringing many thousands of these screen names under his control. This resulted in numerous long-time users losing their accounts, and began a cottage industry of screen name barter and sale.