Anonymous Facebook wins?

Why is it whenever I check my Facebook page some anonymous person posts how much $$$ they won..

most of of the time it’s the games that I’m currently playing.

could it be just a sales/marketing tactic by casino companies?

Hello, I think so. On such platforms casinos are also trying to get some players and if they post similar things, there is a chance that someone will get caught. However, I think it's more of a tactic to get players into a particular casino and I would be cautious about depositing. I would definitely recommend doing some research on the casino before you play there to reduce the risk of problems as much as possible. 

I hope you don't run into any. Good luck. 🙂