First, let me say that some Bogleheads in this group seem angry that others in the group own gold. Why? Why the ad hominem attacks?
Second, explaining the reasons that you believe that gold would not add diversity to a portfolio is more constructive than personal criticism to those of us who are reading to learn something. Quite frankly, I think that gold and bonds are a bad buy right now because of market timing issues. Of course, that goes into market timing. Rules of diversification say that I should buy something other than stock right now. What I have not seen is a discussion about why a gold fund would be bad diversification (say 15% bonds, 5% gold or some such).
Third, as to bitcoins: I am assuming that is gold that you buy to keep in your home. I plan on buying some someday with my "play money" so I can either A) pretend to be a pirate around the house (my wife will love it... maybe) or B) Relive my childhood by watching the Rudolph the Red Nosed Reindeer movie and sing the "Silver and Gold" song. That being said, if it makes someone happy for the above reasons or because it makes them feel more secure, why is it bad for them to buy if they have a fully funded 401k with index funds. What if their hobby was buying art? Also an investment of questionable results. What about having firearms for hunting? Meat is your profit. What about having a Playstation 3 for entertainment? We spend money on lots of things. If someone first invests into a diversified index portfolio (as I am assuming they would on this site), why the harsh criticism for buying the coins? I am certain we all have frivolous purchases. My wife spends hundreds of dollars on makeup and fashion. If I spend my portion of the play money on gold coins, is that bad? What about the BioSolar stock I bought with play money? (Current value is approximately 8% of the purchase price I paid). Gold would be a better investment than that.
Long story short: why is a gold fund not ok for some diversification (Or metals fund)? Why is everyone so angry that some people buy pirate treasure?
EDIT: For the record, this post has both a serious question and a "lighten up guys" humorous portion. It is not designed to offend anyone. I hope that was clear.
I'm not a financial professional. Post is info only & not legal advice. No attorney-client relationship exists with reader. Scrutinize my ideas as if you spoke with a guy at a bar. I may be wrong.