Domains will be disabled, if you don't verify them

Starting next week, when you register a domain with new contact details, transfer existing domains or
change the registrant (owner) or email address on your contact information, you will receive an
additional email with an activation link. If you don't press this link, your domain will be 
disabled after 15 days.

This is actually required by the new 2013 ICANN contract. Not all registrars are on the new contract 
yet, but those that have already signed are required to start following it as of January.

Link: http://www.icann.org/en/resources/registrars/raa/approved-with-specs-27jun13-en.htm#whois-accuracy

You can thank the law enforcement lobby and ICANN wanting to keep them happy. All of us registrars fought
hard against it for a number of obvious reasons, but they went forward with it anyway.

Almost all registrars will be on the new contract soon if they already aren't because ICANN made it a 
requirement to be able to sell the new GTLDs. This is now going to be a normal part of owning a domain