DynDNS dropped their free offering a couple of years ago. If you had created your account before then, you were grandfathered in, and still got 5(?) domains for free; as long as you logged in frequently enough.

Dyn permanently ended its free hostname program in May 2014, with 30-day notice given on April 7. http://dyn.com/blog/why-we-decided-to-stop-offering-free-acc...

Also they wouldn't be able to go against afraid since it's fundamentally a different type of service.

It offers a DNS service for your domain and the ability to share your domain with others.

You can't seize the 100.000 domains being shared and used by bot nets so the only easy target was no-ip.

What i find extremely troubling is the domains being handed over to another corporate entity this mechanism is just ripe for abuse.