the privacy risk of receiving funds from multiple sources to one address or spending from one address to multiple people is where each merchant/sender/receiver to or from that address, where if you offer personal info then associates that address with a name they have. and they can then pass that info on if you keep using that address if it becomes an interesting address to keep an eye on
Yeah, and considering how much companies usually keep of your data, I wouldn't doubt that exchanges are using this on mass. I imagine this sort of data will unfortunately become a
gold sat mine in the near future. Hence why people should care about not willy nilly giving their information to any company or person for that matter, that asks for it.
for sake of humour, im making one small adjustment
a few years ago the company behind bitnodes was doing offers of awarding people sats for handing over personal info. like linking their social media and stuff.
so yea it will be a 'sat mine' linking forum usernames to social media and then to known nodes and wallet addresses.
other services awarding sats for 'learn about bitcoin' are able to give away sats because they sell that info when you sign up, other things like 'refer a friend' too as it brings a bigger picture of who you are by revealing your social connections to others
chain analysis websites earn money selling their data so if they can fill that data with tagged addresses it adds a premium to their data
many exchanges wanting this info to be able to analyse it and learn more about their customer behaviours, is worth alot of value to them.
the more an exchange knows about a customer, the more they can spot suspicious people/behaviours and send SAR(suspicious activity reports) and avoid getting fined for accidentality missing out on suspects that should have been obvious if they had the info to make a good decision to report or not