Speaking as someone who reposts images and articles from skateboarding magazines... always, always, always give as much credit as you can. Think about all of the different people involved in getting that piece of media into your hands. Filmers, photographers, writers, photo editors, etc. all played a part and you should recognize it when appropriate. If you didn't tag a filmer of a clip because you were "too busy", then don't post the clip.
Edit: as a follow-up, another benefit of handing out regular credit is that people who worked on those products will really appreciate it (crazy, I know) and will occasionally reach out and comment or add some insider perspective to what you reposted. I've had a few conversations with Jaime Owens about the BTS of Skateboarder, and with Chris Bywater about being a photo editor there, just from regularly crediting images I've posted from Skateboarder.