"Hagrid not the Half-Blood Prince" Rumor Partially ConfirmedNews
Yesterday Mugglenet posted that two of their readers who attended the Edinburgh Book Festival reported to them that J.K. Rowling revealed in private conversation that Hagrid is not the Half-Blood Prince. We've been able to confirm through a separate source that we trust, that at least one of those readers was definitely at the event.
As for the rest...it's still rumor, but appears to be growing stronger. Mugglenet reports that both readers had separate, UK-based IP addresses and solid accounts of the day's events.