In the meantime, there have been numerous rulings on the question of whether it is permissible to grant customers benefits when they submit ratings or similar. See this article, this article, and these comments.
The Bonn Regional Court has now also ruled that it is anti-competitive, because it is misleading, to offer customers a financial incentive for a Facebook Like. Because the defendant pharmacy in these proceedings offered bonuses if you collected enough “Castle Thalers” and you received these Castle Thalers if you submitted Facebook Likes, new customers could no longer be sure whether the Facebook Likes were “real” Likes and therefore neutral.
The number of “likes” nevertheless already reflects a certain popularity in the general consciousness, which indirectly also indicates customer satisfaction.
This could only be ruled out if the circumstance had been clearly pointed out, as could be the case with online services or closed communities that might be geared towards this.
As a purely precautionary measure, it should be noted that buying Likes via various providers would also be anti-competitive, since these Likes are also not made because the users really like the buyer. The fact that in this case it might be difficult to prove the purchase does not change the legal issue!