How can someone get a single character domain?

Last time I tried to register a domain of 2 characters it told me it had to be of more than 2 characters. How is it possible that paypal has

http://x.com

Is there a special way to go about this? obviously - a.com - b.com c.com are not taken(else cyber squatters would have been sitting on it since the early 90's)

Do you know how this works?

From serverfault DMin

• It was purchased before 1993 by Weinstein & DePaolis, and subsequently sold to Paypal (or the company was bought out). In 1993 IANA reserved all remaining single letter second-level domains, and grandfathered the ones already issued. Other functional, corporate examples domains are t.co (Twitter) and q.com (Qwest).

  I hate to cite Wikipedia as a source, but it has an acceptable article on Single-letter second-level domains:

  On December 1, 1993, the Internet Assigned Numbers Authority (IANA) explicitly reserved the remaining single-letter and single-digit domain names. The few domains that were already assigned were grandfathered in and continued to exist.

  The assigned domains in this group are the following:

  i.net  INet Solutions Ltd     Future Media Architects
  q.com  JG                     Qwest
  q.net  Privately owned        Privately owned
  x.com  Weinstein & DePaolis   PayPal
  x.org  The Open Group         X.Org Foundation
  z.com  HomePage.com           Nissan Motors
  

  As of April 2009 only three domains, i.net, x.com and x.org host a web site. q.com is active but redirects to qwest.com.

  Nick Kavadias : nice answer. Excellent wikipedia para-phrashing

  John Gardeniers : +1 for not treating Wikipedia as an authority on anything.

  Chris Marisic : @John wikipedia is pretty much an authority on EVERYTHING.

  gbroiles : Paypal has had x.com for a long time - it looks like it started being used for a payment system on or about 10/1/1999, per archive.org.

  Chris Thorpe : @Izzy + John - Old-school thinking there folks. Wikipedia is a fine reference source so long as all parties understand how it works and the obvious due-diligence/caveaty that implies. The early 'wikipedia is not reliable' meme seemed to be perpetuated by people who were shocked - SHOCKED to discover that any old joe bloggs could edit it! Horror!

  Wesley 'Nonapeptide' : I find it ironic that searching for "Reliability of wikipedia" on Google returns with the first result as the "Reliability of Wikipedia" article on... Wikipedia. Redundant: see recursion.
  From Izzy

• I don't know how Paypal has x.com, but a.com, b.com and c.com seem to be registered to the Internet Assigned Numbers Authority (IANA), and has been since 1992. Most of the single-letter .com domains are like that except q.com (qwest; since 1999?), x.com (paypal, since 1993?), and z.com (nissan, since 1997?)

  You have to check the whois database to see what's taken and by whom.

  I think the 1 letter domains were taken up by IANA back in 1992 and they made 3 exceptions. And the 2 letter domains are simply all taken so it's simplest for your registrar to tell you to not even bother with a 2 letter domain.

  From freiheit

• I'm not 100% sure but I believe it involves rubbing elbows with verisign execs, being very early on the internet (1993) and quite possibly a lot of money.

  From Joris

• From the book 'The Paypal Wars', page 100:

  It seems that the rumor back in the day was that Elon Musk (current CEO of Tesla Motors) paid $1millon for X.com.

  From Danny Dulai