You cannot cancel your account. However, hidden somewhere in their privacy policy we found this:
If you want to close your Website account and have us delete the personal information in it (except for information that we keep for record-keeping purposes), you should call MLB.com Customer Service at 866-800-1275.
So sadly, your account never really gets removed. We suggest you use the aforementioned number to complain!
URLS:
http://mlb.com
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.