It gets you in their directory, which is a nice place to be. It has no other effect.
If I recall, they do it to reduce their spam-resisting effort, but still review new entries. but I've not checked their site for a liong time.
Some resent the 'intrusion' of having to add the code; personally, I'm committed to opt-in systems, as I believe that no other security has a hope, as spammers and scammers move waaay too fast. I'm still hoping Google will go down the same road!