Do you not recognize how lousy of a video sharing website this would be? Spammers are going to be constantly uploading marketing and other low-quality content with irrelevant keywords, while users that actually put work into making good quality videos will see their results pushed to the bottom quickly. How will you deal with that without implementing a system that can identify and recommend non-spam videos? Even the oldest versions of Youtube were boosting videos that got lots of likes.
>the closest match
How is deciding the "closest match" not considered a recommendation? They all have the user's keyword, what other criteria will you use?