It's a complicated topic without nearly enough exploration in the legal area, and without any real agreement from the companies that run these social media platforms. Twitter's ToS (and their reps) have said you can embed anything without needing advanced permission; Instagram says the opposite. Media outlets use embedded tweets/Instagrams for editorial purposes everywhere, and this seems like it would be fair use (taking a snippet of a 140 character message as you would with an article makes no sense) but some people still complain. No one has any problem with embedding YouTube videos or Vines. How this all plays out is likely to be decided in the coming decades in courts and the media.

Three things that would be incredibly helpful in this area:

1) All these services should give users the ability to prevent embedding of their posts either globally or on a post by post basis. Drawing a very bright line like this makes what is and is not OK very clear. Off or on by default would be debatable.

2) Supply a UI or API for automatically obtaining licensing permission (requester goes to an Instagram post, clicks/taps "request license to use in/on {web, billboard, TV commercial, etc.}" which sends a message to the original poster, poster can than choose to consent/refuse, response is sent to the requester.

3) Make some public statements / legal guarantees (i.e., a promise to stand behind people who get sued even when using service-provided embedding tools) about what they consider acceptable usage.

Right now it's just very gray, and the safe route is to obtain advanced permission for anything with a photo, which I think goes against the frictionless spirit of the old web (i.e., just put up a link or excerpt a post and be done with it.) The service-provided embedding tools try to maintain that spirit in the more walled-gardeny world, but legal uncertainties still make that iffy. I wrote a bit more on this previously: https://medium.com/@sthware/user-generated-content-embedding...

I'm not sure what the legal reasoning would be for "hashtags as consent for photo usage", but something tells me that it probably wouldn't hold up in court if it came down to it.

Edit: another thing that needs discussion is things that seem innocent to many, but could be legally questionable. Prominent example: retweets. Let's say you embed a Twitter widget of your company's feed on your web site's product page. You retweet something someone has posted about your product. It then appears in the feed, on the web site, next to your products. Protected or not? Using some of the logic from Heigl vs Duane Reade, it might not be: https://social.ogilvy.com/celebrities-suing-brands-for-a-twe...