Apple's iMessage Service Is Down
macrumors.comNot just iMessage, it looks like there's massive outages across multiple networks including T-Mobile, Verizon, AT&T: http://downdetector.com
DownDetector is a _very_ blunt instrument when it comes to actually detecting service outages.
It simply tracks keywords on social media. So more likely iMessage is truly down and regular folks just blame their carrier or something.