I'm also one of the Kickstarter backers. The device's bandwidth usage indeed interferes with normal usage of the network. When I contacted support, they told that they wouldn't add a lower bandwidth cap setting.
I had to disconnect it months ago and the device has been stored since then.
The device needs around 400kbps of uplink capacity currently, though we are working to lower that.
In my own home, I'm on the slowest DSL tier that my provider offers, and only have 700kbps upstream. Space Monkey works fine here, and I can still do dual Netflix streams while it is running. Some users will have to manually adjust their bandwidth settings in environments like this.
That's a number we hit on experimentally. Constraining bandwidth below that, currently, causes the network backup part of the system to perform very, very poorly, resulting in your data not getting out to the system in any sort of reasonable timeframe.
This is in part due to factors that we have some control over and can tweak to allows less capable links to make progress (and we're hard at work on this) and partly due just to plain old physics: if you want to be able to push N GBs of data to the network, with some redundancy factor R, and allowing for self-healing of locations that may leave the network due to failure or otherwise H, and also allow some amount of access from other devices in the cooperative network, in some given timeframe T, there's some math that indicates how much bandwidth is needed theoretically, even with everything optimized.
The good news is, I believe we have some wiggle room here to optimize out still.
Not everyone lives in a well connected city; I live in a rural area and we can only dream of 400kbps currently. It's a problem which will not be a problem in the future, however they have been saying for many years now that 'soon' it will all be different.
I had to disconnect it months ago and the device has been stored since then.