Which type of registration is better?

Hi there,
I'm developing a website. Its targetting tutors who are after jobs. Each tutor is given a page containing all his personal an professional information, so that people looking for a teacher can come, search and find the guy who suits their needs.
With the short description given, let me know what do you think about this question:
What kind of registration process is good for the website?
You know, I can simply put a "resgister" button in my homepage and provide the tutors with a form to fill in the blank and join the website. Or I can forget about this kind of registration and only do it by allowing the present members to send invitation emails to their friends and invite them to join the website. Much the same way that Google does it, in Orkut and gmail.
Any suggestion would be appreciated.
Thank you very much

I wouldn't do it through invites personally, unless you can ensure that there will be a lot of people interested.

You can add the ability to invite, but don't make it mandatory.