Boy, this would be a great way to hijack Facebook accounts. Just convince a bunch of people to run your bookmarklet on their Facebook profile.
https://www.facebook.com/ajax/typeahead/search/first_degree....
with 'userid' replaced with your numeric Facebook account ID.
With the "filter[0]" in the url, all scores came back as 0 for me.
There might be another way, but this is the one I use.
It's also a great habit to get into. Reading source code is invaluable in understanding and learning. And it is a skill that can be cultivated just like others. For example, the Prey project is an invaluable piece of software, except it's potentially extremely sensitive. Probably worth reading the source first.
You also start to get very well versed in the "usual way of doing things", especially if it's a language/paradigm you're not programming daily in.
http://cm.bell-labs.com/who/ken/trust.html
To give one example of how this could fail, the server could return different code when the request referer is facebook.