Best way to post videos from ... wherever?

TWebMultimediaControl lets you load videos that are local to the app you're building.

TWebYoutubeVideo lets you load videos specifically from YouTube.

If you want to play a video hosted elsewhere, like Vimeo or S3 or Vidyz, what are the options?

I tried TWebBrowser and set URL to a YouTube video (just because I had one handy) and it displayed an error message saying it could not load from YouTube.

Some hosting places offer you an embed code for their videos, some just let you use a URL that points to an MP4 file.

(Vidyz gives me an IFRAME embedded inside of a DIV tag, for example, that's intended to be pasted on a web page.)

What are some other possibilities to handle these at run-time?

If you get code for embedding, you could add this HTML code to a TWebHTMLContainer

What about TWebHTMLDiv and TWebHTMLSpan?

Why would you choose one over the other?

TWebHTMLContainer as a HTML property with which you can easily set the content. TWebHTMLDiv / TWebHTMLSpan are designed more as control containers.