I definitely support this. I've suggested this before, but considering the opportunity (our first birthday), everyone, including yours truly, seems to have been taken over by the idea of receiving an even nicer gift for the occasion. Or course, nothing came out of that. But hey, one can dream. :)
More seriously though, yes, in my opinion, it could make a nice addition to our site's features. I don't see it as problematic in terms of substantially increasing bandwidth, client or server load (even enabling MathJax isn't really anymore in this day and age not even on smartphones), and it's definitely possible. Some other Stack Exchange sites (including beta ones) already have similar implemented / enabled, for example Video Production has the ability to embed YouTube videos and SoundCloud audio streams directly in posts and through links alone that are then parsed and videos in links embedded on submit (that means no preview during editing tho).
There is however a slight concern that enabling YouTube video embedding within our posts might lead to increased frequency of low quality contributions where videos will be used to substitute written word, or even to promote one's own YouTube channel or help spread video annotations and descriptions spam. This is something we should be vigilant about during our peer reviews and demand quality just like we always did. Also note that while displaying embedded video thumbnails and the player alone isn't too bandwidth demanding, playing long ones to review their contents or follow the contribution's narrative might be to some, especially those on bandwidth throttling, download capping or PAYG mobile carriers. So here's a few ground rules I believe are reasonable and we should all abide to (including yours truly):
Don't embed videos as centerpieces of your contributions and include transcripts!
Not everyone will be able or will have the time to watch full-length videos you'll be embedding. We also want answers in text and explaining what the video you link or are directly embedding will present and how is it relevant to what you're trying to say in your contribution. Including a video should never serve to replace a properly written question or answer, it should merely complement it and make it easier to understand! Rule of a thumb here is that your contribution should still remain valid, complete and comprehensible even if the video becomes unavailable at a later date.
Remember to attribute video's source and authorship, just like you'd do with images!
Not every video embedded will require this, but please check with your source if that's the case. Last thing we want to enable with this is content theft, abuse of authorship, disrespect publisher rights or distributor's terms of service. Just because some video is easy to embed, it doesn't mean that we're at liberty to do so. Also note that some materials can include copyright flags, demographic or other restrictions at a later than publishing date and won't play in embedded players anymore because of this. If you think that with some video it sounds too good to be true to be available without restrictions for everyone, it probably is. Please follow up on posts where you included such videos and respond to comments notifying you of their unavailability.
Not every linked to video needs embedding, we can still link to them in text only!
Some linked videos will only serve as an additional point of reference, aren't following the narrative of your contribution and, if they were displayed all over it, would detract from its true purpose. Please only use embedded videos where you deem are absolutely essential to what you want to present in your contribution, or, as an alternative reason, they use a video preview thumbnail that you'd include in your answer anyway for illustrative purposes.
Avoid embedding videos of poor quality or ones that promote products or services!
This includes videos that use excessive number of in-video annotations that link to other pages, videos that are primarily made to attract attention to the YouTube channel they were posted on, videos that are otherwise too pushy in any respect, that are of poor quality (inaudible, unable to see much, too loud,...) or are too lengthy and most of their contents aren't relevant to what you'd like to show us. Note that most popular videos are also republished to include spam or promote other non-relevant causes. If you can, find the best quality original, from a trusted publisher.
Watch out for shaddy, low rep publishers, and inappropriate content like "video bombs"!
Please watch the video in full before posting it on the site, embedded or not, and pay attention to inappropriate contents. That includes the so-called "video bombs" or the publisher being prone to replacing video preview thumbnails with inappropriate ones at a later date to try and bring additional attention to them. If you're unsure, look through the publisher's channel, sort by most popular videos, and see if any of them seem suspicious in that regard.
If there's only a part of the video that's relevant, please embed it with a time link!
Sometimes, you'll want to show us a short part of an otherwise lengthy video. It will be possible to embed videos so they start playing at some specified time, please see below how to do that:
Together with @AJ Henderson, moderator on Video Production, we've also tested this parser's ability to display YouTube videos and start playing at specified position. Sadly, this doesn't work via a
# URL hook as YouTube gives addresses to videos when you click on its Copy video URL at current time link, but simply replacing the
# hook with
& to add a new parameter to the URL does work. Here's a working example of that.
I've also asked about this our Community Manager (quite some time ago) and, if I remember correctly, we simply need to ask for it like we did to enable MathJax. We currently don't have all too many posts linking to YouTube videos, but reading some, it would certainly make them easier to follow if readers didn't have to open a new tab / page in their browsers. So yes, I'm in it. And with your support, I'll be on it as well. ;)