This is going to break in cases where the request line grows above 8k-16k. Many browsers/proxies implement limits on headers/request lines, for good reasons.
This is quite clearly covered in the actual document!
> For longer documents, Hashify splits the contents into as many as 15 chunks. The chunks are then Base64-encoded and sent to bit.ly in a single request. The bit.ly hashes contained in the response are then "packed" into a URL such as http://hashify.me/unpack:gYi2Ie,g4fpte. Finally, this URL is itself shortened.
It's a very cool idea though.