Regulations will probably come in the form of making these types of checks mandatory. See, for example, how US Senators pressure payment providers to check up

Regulations will probably come in the form of making these types of checks mandatory. See, for example, how US Senators pressure payment providers to check up on whether their customers may be profiting from illegal file-sharing: https://www.leahy.senate.gov/press/judiciary-chair-leahy-urges-visa-mastercard-to-recommit-their-efforts-to-address-illegal-activity-online https://www.leahy.senate.gov/press/judiciary-chair-leahy-urg... If Dropbox-style hash checking of files could be seen as the standard in the industry, I can see how failing to do that could be seen by a court as potentially negligent.