I used to be against having any significant amount of gold in a portfolio because it's not a "productive" asset. Companies earn profit, bonds pay interest, and real estate gets rent checks, but gold costs money to store. "Productive" assets get you price appreciation + income. Even companies that don't pay a dividend are investing trying to grow, hence your profit comes partly from economic activity, not just a bet that people will pay more money for the exact same thing tomorrow.

Now that many bonds aren't necessarily meeting my definition of a productive asset (small or negative yields for the safest bonds in Europe), I'm backtracking on my stance. The zero-interest rate world is weird.