Facebook’s annual F8 developer event kicked off today, and the company has had a number of pretty big announcements. Among them was information about plans to build a dating platform right into its mobile apps – investors in Match Group, which owns a whole bunch of online dating services, including Tinder and Match. com, have not taken very well. As of this writing, the company’s shares are down more than 20%.

MTCH took a pretty big hit today.

In addition to Tinder and Match.com, Match Group owns OkCupid and PlentyOfFish. A sharp drop can be seen in the Match price chart as of 1:20 p.m. EST, just as Facebook announced. The decline slowed about 20 minutes later, but the price continued to fall, albeit more slowly.

Facebook dating profiles will be separated from regular Facebook profiles, and dating activities will not be shown to Facebook friends. Potential matches will be recommended based on a number of factors, including mutual friends on the social network. The service is still a while; testing is expected to begin “later this year”.

Facebook is finally ready to roll out Dating to a large audience. Starting today, the service will be available to users in the United States, as well as those in Argentina, Bolivia, Brazil, Canada, Chile, Colombia, Ecuador, Guyana, Laos, in Malaysia, Mexico, Paraguay, Peru, the Philippines, Singapore, Suriname, Thailand, Uruguay and Vietnam. An expansion in Europe will follow, but that could take until early next year.

The Facebook Dating opt-in allows users to create new dating profiles, separate from their main Facebook profile. By default, users will not be matched with their existing friend groups, although a “Secret Crush” mode allows you to quietly test romantic waters without revealing your feelings. Instagram posts can already be added to dating content and support for stories will be coming soon.