Exactly this. MSBlast was so prevalent that ISP's would prevent infected computers from accessing the internet, by redirecting them to a page which described how they could remove the infection and patch themselves up.
I don't remember that happening with any other type of infection.
And I don't think we'll ever see that again. Even if there are big vulnerabilities in Linksys, DLink, Netgear or common ISP shipped modem/router combos - there are just too many different devices to see it on the same scale.
I don't remember that happening with any other type of infection.