I am one who's been receiving these emails also, and based on the email address & password, I assumed it was this site (or a computer/network I used to access the site). I sent something into the support team only a day or two before this announcement. I received a reply stating how the passwords were stored, and that they were still going to investigate and be sure. I then later received another message pointing me to this thread. That was FAST, and responsive!
I've received a ton of these style emails using other email addresses and passwords I use on other sites as well. Some I recently receive include passwords I have not used in years. This stuff does happen sadly. There's only so much everyone can do. You can have the best anti-virus software ever dreamed of, and if you are the (un)lucky one to catch it first, your anti-virus will have no clue on it and you'll be infected, dealing with whatever damage it does.
I do think RadioReference handled this issue quite well. As mentioned by an earlier post, how long do banks or other major businesses take to tell you of breaches. The data in those instances are a TON more sensitive than what is here. Think about bank, health, etc records. Also, I don't know about most of you, but I get to use this forum for FREE and so can everyone else, even without creating an account! Those banks and others you pay for and expect security. This is just a simple site.
Furthermore, of any of you who did receive similar emails, how many even reported it? How can they fix a problem they don't know exists? Same thing with the virus example, how can the anti-virus block the virus unless it knows the signature?
It was a vulnerability. There are people out there trying to find these all day long everywhere. You can do everything you can, but there may still be something out there out of your control that has the issue. Maybe the hosting service, maybe the db system, could be some other thing.
Again, I believe RadioReference did a great, speedy job of taking care of this. I've appreciated this site before, and I do even more now. It sucks it happened, but it did, they did what they can to prevent the same exact thing from happening again.