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I believe @dkbit98 wanted to say about the page speed and not the bandwidth. And it's true, a page with a video embedded decreases the page loading time. It must be horrible for users with a smartphone/tablet
Bitcointalk has surely an 'unlimited' bandwidth and saves a lot by using Cloudflare, so the problem is not here.
(*unlimited is a marketing trick from web hosting companies most of the time)
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I don't know if it's still possible with Youtube, but instead, to send bots traffic to your video link, people were able to cheat the system by embedding it into a page (a forum is good since they don't pay the hosting) and then to send traffic to the thread link via autosurfs and alike