Yahoo is now owned by Verizon, of course. The lawyers have gotten around to screwing over their customers, probably partly because of the new European privacy rules.
Yahoo has an abysmal record on security, which I can attest to personally.
Amongst the other changes forced on users are mandatory arbitration, waiver of rights under class action lawsuits, and for a commercial customers – filing a statement that they will indemnify yahoo/Verizon from any lawsuits resulting from their customer’s Operations.
They appear to have borrowed the Facebook strategy to prevent people from canceling their accounts. Once you initiate the account cancellation, a 60 day counter starts. Any subsequent sign in (like a device accessing your email account) revokes your request for account cancellation. In order to request cancellation again, you have to log to your yahoo account. After they acknowledge your cancellation request, you are forwarded to a page that is going to automatically log you back in.
AOL is also owned by Yahoo – this strategy to prevent account cancellations is very familiar.