The Like button is synonymous with Facebook. It's the social network's defining feature. In the past year, people have moved away from the Like button in favor of custom actions. People can now "favorite" or "heart" content they like. Facebook now wants to bring those custom actions back under the Like button.
Facebook announced today that all custom actions inside apps must now go through the built-in Like action. Your apps can still use the custom action, but it has to be tied to the Like action instead of just a custom action. They claim that the change will allow them to "present stories in engaging and consistent ways across news feed and timelines."
Thankfully, the update isn't a breaking change. Developers can keep on using the current custom actions as they have been. The change only applies to new custom actions and ones that are resubmitted to Facebook. With Facebook's new push into mobile, it only makes sense to tie the Like button into the custom actions that populate most Facebook connected mobile apps.
The change may also be indicative of a major push into mobile advertising. They already have Mobile Ads for Apps ready to go. A major indicator of a Facebook's page's success is the number of likes that the page and its content receive. Being able to convert more actions into Likes would only further please advertisers.
Developers can check out the documentation for all the details on associating custom actions with Likes.