That is a good point: "The Bitcoin network is by far the fastest distributed computing network in the world. <ref>{{cite web |title=Block 0 - Bitcoin mining network speed estimate |url=https://bitcointalk.org/index.php?topic=38064 }}</ref"
However, if you want to keep the Bitcoin article in a professional shape, you should avoid vague definitions, such as "by far". Numbers should be given that prove your position.
I don't think it should be noted on the top part of the article, either, since it is not a defining characteristic of Bitcoin. It would look better in a section about mining, related to P2Pool and other pools.
Finally, a reference to a forum is never trustworthy for Wikipedia, and any editor is authorized to remove it, if that is the case.
I agree most newbies get their first impression about Bitcoin from Wikipedia. So it should always be kept as professional as possible.
An example of a well written article about Bitcoin is in the German Wikipedia:
http://de.wikipedia.org/wiki/BitcoinIn section 5.4. Rechenaufwand beim Mining, it explains the computing effort in mining, and how it compares to supercomputers around the world.