For example, your forum is private and someone clicks on a particular thread. They get redirected to the log-in page which says something like: "Here is snippet of the post you just clicked on (show snippet here). To get immediate access to the rest of the thread, please login or register below. (login/register box)"
The top login drop down box would be disabled and everyone would be sent to this page: http://xenforo.com/community/login with the teaser snippets.
I think this would be a great idea to help entice members to join and give them a taste of what's inside the site without seeing the whole thing.
You can see an example of how "snippets" can be used here:
Notice the tan box which is pulling an excerpt from a thread I clicked on. The login box is below it.
Screen capture of what I am referring to. Can this be "teaser" concept be done in Xenforo?