Why doesn't Google's “I'm Feeling Lucky” feature work in this specific case?

Question

Why does this work:

http://www.google.com/search?q=azure+ray+site:en.wikipedia.org&btnI=I%27m+Feeling+Lucky

And so does this:

(Note: loads YouTube video) http://www.google.com/search?q=azure+ray+rise&btnI=I%27m+Feeling+Lucky

But this doesn't:

http://www.google.com/search?q=azure+ray+rise+site:songmeanings.net&btnI=I%27m+Feeling+Lucky

Nor does this:

http://www.google.com/search?q=azure+ray+rise+songmeanings&btnI=I%27m+Feeling+Lucky

Can websites/domains disable Google's "I'm Feeling Lucky" feature? Or what?

[UPDATE]

As mentioned in the comments, when both search queries that do not work using those URLs are typed in manually on the Google homepage 'I'm Feeling Lucky' does work (note that you will have to disable Google Instant to use the button). However, when I copy the resulting Google URL (captured using Firebug) and paste that in the location bar it still doesn't work. An example full URL is:

https://www.google.com/search?hl=en&site=&source=hp&q=azure+ray+rise+site%3Asongmeanings.net&oq=azure+ray+rise+site%3Asongmeanings.net&gs_l=hp.7...3487.3487.0.6936.1.1.0.0.0.0.139.139.0j1.1.0.les%3B..0.0...1c.KclWi-RBGlo&btnI=1

Answer 1

I just noticed the question "Google's “I'm Feeling Lucky” URLs no longer working?" under related in the right navigation bar. The second answer to that question offered a working solution: add the querystring parameter sourceid=navclient (navclient is a reference to the Google Toolbar):

https://www.google.com/search?q=azure+ray+rise+site:songmeanings.net&btnI=I%27m+Feeling+Lucky&sourceid=navclient

[UPDATE]

Apparently having your Referer set to *.google.com also works. The links in this post of mine on the Google Product forums all work as long because the referer being sent with the request.