The paper with the actual proof (making this a theorem and not just a conjecture or vague speculation) is here:

http://lpd.epfl.ch/sgilbert/pubs/BrewersConjecture-SigAct.pd...

This is surprisingly readable, and the introduction is quite good. In addition, here is a blog post that talks about the terms, their meanings, various implications, and the proof:

http://danweinreb.org/blog/what-does-the-proof-of-the-cap-th...

Finally, despite the shaky start, this is also a good read:

http://www.julianbrowne.com/article/viewer/brewers-cap-theor...