Probably...

I don't know about "every major organization," but there are definitely spies in most industrialized countries. Hence why you have so many numbers stations for them to communicate with each other!

I'm not a conspiracy theorist, but this sounds plausible to me. Companies would have an incentive to spy on other companies. I don't know. I doubt they all have government spies, though.

Government spies? Maybe, depending on what the company does. (No one’s interested in sock-makers, I wouldn’t think.)
Corporate spies? Definitely. Even sock-makers have competition.

I don't know about 'every' but yes, feds are planted all over the place - when the Trumpers stormed DC on Jan 6, feds were fighting with planted undercover feds who had infiltrated those groups and they didn't even know about each other - and those feds are planted specifically to encourage illegal activity and provoke violence so those groups can be raided and have their wigs split

It is totally unnecessary to put spies where all info is readily available, isn't it?

No.