When they delete a GROUP, they also DELETE the OWNERS of the group. All of them. No questions asked.
Therefore, as a group OWNER, take caution! Create a second account for each group you own. Assign OWNERSHIP PRIVS to that Yahoo ID.
Change yourself to a MODERATOR with full privileges (which gives you the same access as OWNER, with the exception of making someone an owner!!) -- you even get the e-mails sent to "lost owner!"
Should a group be deleted then, you will only lose the Yahoo Account that is associated with the ONE group that was deleted -- not your Yahoo IM lists, address books, e-mail account, access to your online banking, Yahoo Wallet, etc., etc., etc.