I’d be curious to know how receptive, or not, these devices are to 3rd party firmware. Obviously this doesn’t help Joe User much either way, since he probably bought an ‘appliance’ because he didn’t feel like, know how to, or know that he had an option to, mess with zigbee-on-embedded-linux; but from the geek perspective(either owner, or someone who might pick one up on ebay) there is a big difference between “Yeah, servers are down; but you can still make it do your own thing” and “Yeah, servers are down; and the only payload cryptographically blessed to boot on the device relies on the servers; so STFU, DIAF.”
Also, when dealing with ‘cloud’ devices, there is an argument to be made that the mothership’s servers and whatever it is they do really ought to be included in the block diagram as equals of the rest of the components: if the device doesn’t work when example.com’s API disappears, is a box labeled “example.com API” connected to the system by TCP/IP any less valid than, say, a flash chip connected to the system by an MMC bus?
Also probably worth thinking about the difference between what one might call ‘user serviceable’ “cloud” devices and “cloud” devices that are effectively captive to the supplier forever(either because of cryptographic enforcement, because the ‘cloud’ magic that they require is simply not available anywhere else, or both).
A cellphone, say, isn’t going to be doing much cellphoning if the carrier goes belly up. However, as long as it isn’t SIM-locked, it’s pretty trivial to instruct it to seek services from some other carrier, and there are standardized mechanisms for doing so. Same with cable modems, email clients, etc.
Other ‘cloud’ things; Not So Much. Sometimes it is just a matter of lock-in. The ‘cloud’ portion might be little more than a thin candy shell over an HTTP or WebDAV or similar server; but if it is hardcoded to only work with the vendor’s SSL certs, sucks to be you(and, if the ‘cloud’ is battle.net, the vendor might go tactical nuclear asshole on you and argue that merely creating an interoperable 3rd party implementation is illegal because the DMCA. Not hypothetically or anything; seriously, fuck Blizzard. In other cases the ‘cloud’ portion may be a fairly giant pile of proprietary algorithms for which no real replacement exists, but there may be nothing preventing you from shimming in the best substitute you can find.