For example, companies/online retailers who screwed up my order or irritates me with repetitious stupid promo deals especially the promos/coupons/codes that excludes the stuff I want, people who pisses me off, or even someone I just don’t happened to like for no particular reason, I put their legit emails in the junk/spam folder. 
Probably it doesn’t do anything (if not sabotaging spam mail screening processes) but it satisfies me. How about you?
eMail I don’t want is junk by definition. Anything I don’t want for any reason gets the junk treatment.
“Junk” maybe, but not necessarily “Spam”, as Gmail & Yahoo mail call their junk folders, “Spam Folder”.
Some of these are from people I know and emails are legit emails, not spam, that I happened to opt to ignore. Do spam informations gathered from individual email accounts get passed onto larger central spam data files?
Yeah. I run an email newsletter service. We subscribe to services from AOL, Comcast and I think maybe Yahoo called “feedback loop”. Any time an email goes out from our server and gets put into a junk box we receive a copy of the email from AOL (or Comcast or Yahoo) with the recipient’s address redacted. One of our people goes through all these emails and clicks the unsubscribe link that was sent out in the original email.
I’m sure not all bulk mailers do this, and having the email redacted is a pain in the butt, but the service is really there to let the SMTP host know that their users may be spamming.
That’s good.
At least the businesses that I’ve patronized for long time should notice my displeasure.