I hate being captured and I never captured.  I did, however, allow them to sign up for updates.  I had plenty of business.  

I've recently switched my settings to allow prospects to view unlimited homes without registering. The more I thought about it, the info is freely available on several major portals, so I would rather have someone keep using my site (and hopefully build some likeability and trust) rather than drive them away with forced registration.

I have never required prospects to register. They will simply move on to another site.

I have experimented both ways and forced registration after 3 views worked the best for my sites. Forget personal opinions and test.

RealtyZap + my Market Leader site asks for information on 3rd listing.

Great question. I don't like giving my personal info to see information. 

I don't force any capturing and do not like sites that do. People sign up on my site to be able to save different searches and get set up their own schedule for email notifications.

No registration unless you want to save your searches. Many do, but they don't have to.

They can get basic information but need to register for detailed information.

Do people give real contact info when forced?

RealtyZap + I close $3-$4M annually from my wordless site.  I've tested extensively and you will get more opportunities to sell with forced registration period.  

I don't capture, my IDX search doesn't allow for it (free one from the board).  No one uses it, so I'm not concerned.

They can look at 3 properties before they need to register.

Yes

 Good morning. I've seen IDX's structured in many different ways. Some will allow two or three searches before they have to register, while some have other criteria.

Registration is not mandatory.