How much of this is "building an audience" For example Paypal pretending to be legitimate buyers and purchasing eBay goods but only via paypal? Or reddit posting stories and comments under sock puppet accounts?

If this was a clear impersonation of a specific individual then it is a serious fraud (presumably the company expects financial gain). If it is "These guys are amazing - A Fortune 50 CTO" then half of Hollywood does it every day.

I think that morally overdrawn is the natural state of much of the business world - morally bankrupt is rarer.

So for some actual advice - if it was a crime, report it and leave. If you cannot stomach the ethics even if it is not criminal, then prepare a good resignation letter and leave - but I would counsel that in doing so you are setting a tremendously high bar for your future behaviour - which is a good thing but it has implications. I would suggest making a public note on your leaving and reasons maybe on your blog. no point in being ethical if no one notices.

but lastly I would look inside yourself - are there any other reasons why the last three and a half years have upset you? What decisions did you not agree with - what relationships have gone sour? Is this all plain sailing then one horrible fraud? if so it seems out of character for the company? if not then what things have lead to this - for example this sort of behaviour is usually seen under real stress, so why did the company end up not getting the sales last year, what shortcuts in engineering have lead to a lower product, what lack of marketing ab tests lead to lack of a sales pipeline?

This maybe the right wake up call the company needs to turn around - do you want that? Or do you think this is not a wake up call but the last straw?

I am rambling on but I have found many ethical decisions rarely come out of simplicity and rarely have simple resolutions.

good luck