[AtteLynx]

I became a registrar for .fi because I was tired of dealing with other registrars. I only provide domains for myself and my friends, but it's still easier, cheaper, and more secure than going through some third party.

That being said, I have no personal experience with other TLDs, but based on a bit of searching some do seem quite easy to become a registrar for.

[cisanti]

That is very interesting, can you give an estimate how much (more) does it cost to you be a registrar and own domains? Compared to random ones. I guess .fi is a bit more expensive than .com anyway.