OpenSea users have started to get blocked, most likely due to their association and interaction with Tornado Cash.
The renowned crypto artist @CloutedMind, who is well-known within NFT world, tweeted about this. He also pointed out that even the wallet vitalik.eth was affected. Yes, that's Vitalik Buterin.
As a reminder, Tornado Cash is an open-source cryptocurrency mixer that obscures the relationship between the original and final wallet by shuffling cryptocurrency among addresses.
Apparently, the timeframe in which wallets interacted with the well-known mixer doesn't matter. Even those who used the platform before the introduction of U.S. sanctions are likely to have been hit by the ban hammer. All of this happened under the auspices of OFAC, the U.S. Office of Foreign Assets Control.
The tweet's author is also worried that other DApps might resort to similar actions, willingly or not – an average user doesn't really care about the reasons behind such measures.