Interesting. I've had my Yahoo account for pushing 20 years. Actually a 15 years they sent me an email saying "thank you for 15 years with Yahoo."
I've never had my account corrupted, or cracked... but then I am pretty crazy about changing my password. Funny thing is I don't use the account for anything serious (I have a real email account for that)... As an aside my YAHOO account is my default account I give out when a vendor, or potential spammer asks for my email addy. I have my spam filters set on it, but I can't remember the last time any SPAM made it to my INBOX on there. I DO get a lot to my "SPAM" folder, but their filters are best I can tell 100%. Something I strive for on my own servers.
All in all I think Yahoo is a stellar service that costs $0! Hard to beat that. The 2 gig storage size is pretty good as well considering.
Always a good idea to rotate passwords on a regular basis.