On one hand, this is already data that Tinder had access to; people have been able to connect their Spotify and Instagram accounts to the service for awhile now. Tinder is simply putting the information from these third-party services into one convenient place.
Presumably, though, Tinder will be adding additional social networks in the future, as this test program expands. All of a sudden, it becomes a convenient way for people to creep on and stalk people they don't know. The idea behind it is to give your matches more substance, interacting with their social media posts on Tinder, which is fine in theory. The problem is the amount of data it could end up aggregating in one place.
According to Tinder, this feature will only work on the people you've swiped right on and have also swiped right on you, not on everyone. Additionally, people do have the option to manage what they share with matches on their Feed. It will be interesting to see how this feature develops as it goes through testing, but it's fair to say we have some reservations.
Update: This article was updated after clarification that this feature only works on people who have mutually swiped right on each other, not just people you have swiped right on.