As we all should know. YouTube is practically built on advertising. So many videos are plagued with advertisements that you have to watch before getting to your video. Yes they are extremely annoying but companies pay a hell of a lot of money for them. It cost $ 175,000 (roughly €135,000) per day to keep ad's circling YouTube. The other way that companies like to get there brand out there by using product placement. This is by now means a cheaper way of advertising but it is just as effective
Think of the most popular YouTube channels you know. The likes of 'feddiew' and 'Epic Meal Time' always have some form of product placement. This can be done with subtlety or not. These YouTube channels can potentially get thousands of views every day. That's thousands of people seeing your product being used my people they respect enough to devote their free time to every single day. Worth the money.
This is one of the advantages of being a YouTuber. You can show off these products in whatever way you see fit.
YouTube help has a full page about product placement and can help any company to apply for paid product placement. You can find this page here.
http://support.google.com/youtube/bin/answer.py?hl=en&answer=154235
As if that didn't make it easy enough for any interested companies, YouTube has a list of the most popular YouTube channels in terms of views and subscribers. Using this, anyone can see what channels would give you the most publicity for your product. The vast range of channels give the opportunity for the companies to see for themselves which channel would suit their product and marketing style the most. Example? Many of Freddie Wong's viewers are interested in movie making themselves and would be very interested in the type of equipment he uses. So a move a company could make would be to ask Freddie to use their equipment to film and edit his videos.