hotmail and yahoo blocking gmail invites?

slashdot are reporting that hotmail and yahoo are blocking gmail invites or at least putting them in the junk folder, and hotmail are doing this to gmail normal email too. i actually noticled some email i would sent to my self from my gmail account to my hotmail account ending up in the junk bin. wonder is this accidental? you wouldent know. gmail are scanning email servers for some reason. maybe hotmail and the rest are worried about this? hmmmm. dont know.