Valve rolled out an update for Dota 2 that restricts watching matches of very high-rated friends. If someone sits above 8500 MMR, you can no longer start spectating them via the "Watch Game" option — Valve frames this as the first data-protection step for top players, whether you buy that or not. FYI: DotaTV is untouched, and DotaPlus training still works as before.
On a separate note, the devs corrected an error in the tooltip for Io's 15th-level talent. The description used to show the wrong damage amplification for Spirits, while the actual in-game effect was already correct; the text has now been aligned with the real values.