Well everybody, it looks like the free ride is over: carriers in the US have started to seriously crack down on Android tethering apps. Head on over to the Android Market site and try to install an app that turns your smartphone into a WiFi hotspot -- there's a pretty good chance you'll be told, "this item is not available on your carrier." We checked out a number of different tethering options and they were all blocked by T-Mobile and AT&T, which isn't entirely new. Verizon has also joined the party and, while it missed at least one that we spotted, we're sure they'll all be gone in short order. Only Sprint has decided against banning such apps... for now. It looks like you might have to finally cough up for that tethering plan you've been desperately trying to avoid.