Ask: Reducing web app barriers vs comment spam?

Hello,

I'm building a new app that will have your standard cold start problem. In previous ventures I have witnessed people (through analytics) clicking to participate then bailing when they find they need to create an account.

What should be taken into consideration when designing an end user web application to reduce participation barriers.

A few options are.

1) Let anyone contribute anonymously in the beginning but monitor all messages for spam.

2) Do #1 but take an email address on good faith so I can attempt to get them to register a a later date.

3) Rely on facebook, twitter, oauth? There is still a price for this from the user's perspective.

Any other options I am missing?