FrontierVille -- if you give a little, you get a little. In this case, that means if you're willing to give up a little privacy by allowing the new pioneer-themed Facebook game send you emails, you'll get a free horse for your land.
If you want the free pony (and who doesn't want a pony?) -- here's what you gotta do. When you load the game, keep an eye out for a pop-up notice from Pioneer Jack asking for your email. If you agree, you will receive an email with a link that will give you a new horse. The email came right away and looks like this (see image below).
Many have complained that they signed up to receive FrontierVille emails and did not receive the horse. If that's the case, you should try signing up for email again or, alternately, try your luck at clicking the following link.