I doubt loading 10 or 20 video previews will really do much to the forums performance since you're loading from very high performance servers. I understand the logic I just don't think it's really that much of a problem and you can't always go by worst case scenarios. *Also I'm fairly sure the previous limit for videos was 2 and I don't recall things breaking.
For me it makes less sense forcing someone to make 3 separate posts if they want to post 3 videos than to just allow 2/3 in one post, especially when it's relevant to the topic at hand and you're trying to put together a good amount of content. Considering this is a gaming site this type of media should be important.
Anyways, I get it, I just likes me my multimedia contents.