McAfee desperately needs some PR help on this one. It will be much better in the long run to put a large, prominent announcement on the their site linking to instructions, etc. Even better would be an 800-number so that affected customers could call and be walked-through the process of fixing their PCs.
Yes, this would hurt the bottom line, but it is just good business.
Why? In a matter of days even the most computer savvy of folks will have put this behind them. McAfee will still be bundled with Localtown-ISP or installed on the new desktops. Mom and pop will see that their "subscription" is about to expire and won't even wonder if this was the program that broke something with svhost.exe.
While you and I may agree that it would be good business for them to go out of their way to fix this and clean up their image, I just don't think it really matters in the long run. I would be surprised if they do anything other than, "Whoops. The next signatures are here".