If someone is willing to watch an entire game rather than play it themselves, they probably wouldn't have bought it anyway. I'd say LP's actually increase a games sales more than they damage it, even for games in which the story is a major focus.
The first episode of PDP's let's play of TLOU has 9 million views and maintains several million per episode after that, yet all those views hasn't stopped TLOU from selling 6+ million copies in less than a year (putting it ahead of every entry in the Uncharted series, which is quite the accomplishment.) Can't say his videos are my cup of tea, but it gets the point across.








