The 10 second feed PUT limit algorithm has been improved.

The old algorithm had several issues related to it including:
1) Sometimes there are multiple sensors behind a home or business router (which is the outward facing IP address) that need to upload every 10 seconds.
2) Random events can happen within the 10 second period and need to be pushed up as soon as they occur.
3) Some services like Electric Imp and SmartThings run in a cloud and share outward facing IP addresses (a bunch of cloud servers).
4) If a sensor uploads every 1 minute, and the http call takes around a minute (for whatever reasons - it happens). The next sensor upload could happen within 10 seconds and GS will reject it. This is actually a common scenario.

We've made these improvements:
* The ten second limit is now enforced by allowing 12 calls within a two minute period. The periods are not rolling - period one starts at midnight and ends at 12:02. This still imposes a 10 second rule, but gives some flexibility to allow some calls to be back to back which helps with numbers 2 and 4 above.
* The outward facing IP address is now combined with the authentication token (either the session or api_key tokens) when the 10 second limit is being validated.

X-Forwarded-For is still supported and will still be needed for some scenarios such as number 1 above (when batching is not possible) and possibly number 3 depending on the cloud service and the number of sensors per user account.