This is what repeated forks (where the network splits and both networks remain viable) will look like to the investing public. Two slightly different cryptocurrencies splitting, then minting coins on both forks at twice the original rate. That looks exactly like money printing.

Granted, decentralized currencies don't have the authority of fiat, so the market could kill off unpopular forks. But it's possible that many, many forks resulting in many network splits could survive. And that means a lot more than 21 million "bitcoins" (depending how you choose to define them) in circulation.