What I hate most is when Youtubers do a top 10 rare list, or something to that effect. They bring attention to things that are already rare, causing the prices to go through the roof. I think this is irresponsible. When something is rare, people's instincts are to gobble it up as fast as possible. It only takes a few bidders to make a price jump up.
If they are just reviewing a game, then I'm fine with that. I do this myself in my own Youtube reviews. I never mention rarity.
I don't think Ebay makes games more expensive, since it increases availability, but I could be wrong. There are plenty of games on Ebay that don't sell, even for $4.
General and high profile video game topics.