Are keynote talks being purchased? I recently listened to a talk given by Brian Lunduke about problems that GNU/Linux are currently facing. In it (roughly 26m48s into the video) he mentions that keynote presentation time slots are being purchased by companies at GNU/Linux conferences. That is, companies are paying the conferences in order to get to be keynote speakers at said conferences.

This made me think, does this kind of thing happen in the academic world too? Are there serious conferences (that is, not the type of conferences we so often get spam emails about) where some or all of the keynote talks have been chosen due to some company/organisation/person paying the conference money in order to get their person to speak there? If so, is this disclosed to the conference participants in any reasonable way?
Some conferences exchange corporate sponsorship for various perks. Those perks may include a keynote speaking slot. Thus, 


This kind of thing happens in academia.
Perhaps more so at serious conferences, because those conferences are more attractive to sponsors.


Perks may be advertised, e.g., on web pages soliciting sponsorship. Hence, 


This may be disclosed to conference participants.
But, possibly not in a reasonable manner, since participants would need to discover sponsorship perks.


Some perks may be privately negotiated, without disclosure to conference participants.