A few months ago, I spent a couple days reverse engineering the Snapchat protocol and wrote a quick and dirty library to use it in your own PHP apps:

https://github.com/tlack/snaphax

Today Snapchat has written me requesting that I take it offline:

    Hi Thomas,
    I'm writing to ask that you remove Snaphax from github
    and no longer publish or distribute it. Snapchat does
    not permit third party software to access our API and
    we consider Snaphax to be an unlawful circumvention 
    device under 17 U.S.C. § 1201(a)(1).

    Please confirm that it has been removed by end of day
    Monday, July 22nd.

    Thank you,

    Micah Schaffer
    Snapchat, Inc.

I haven't had much time to really finish Snaphax (and I doubt I ever will) but I strongly support the idea that third party software should be able to interact with the services I use every day.

I am under the impression that reverse engineering is still protected under fair use doctrines. Is this the case? How should I respond, if at all?