http://www.macworld.com/article/162024/2011/08/facebook_shuts_down_deals_boosts_photos.html

“We think there is a lot of power in a social approach to driving people into local businesses. We remain committed to building products to help local businesses connect with people, like Ads, Pages, Sponsored Stories, and Check-in Deals. We’ve learned a lot from our test and we’ll continue to evaluate how to best serve local businesses,” Facebook said in a statement via e-mail.

However, interrupting visitors is different than providing the opportunity for them to continue their journey (avoiding a dead end). Continuing their journey involves offering added value at strategic points on your website, which can actually enhance the perception of your company. So what I would do is look for other areas on your site where you can ask people to join your mailing. At what point would visitors be most interested in requesting more information about your company? Perhaps they’re interested when browsing products pages, where you could place a sign up form that asks visitors if they would like to stay updated with news & product updates. But certainly not when they’re trying to leave your site.