There are a surprising number of similarities between Bitcoin and SMTP. Both protocols are intended to be decentralized and to transfer things - value and mail. Their creators envisioned a world where people host their own wallets and email servers. This way no powerful actor can unilaterally disrupt the network.
But, market dynamics keep pushing toward centralization. Because most people (including me) aren't confident in their abilities to securely host sensitive information, we outsource these responsibilities to firms like Mt. Gox, Coinbase, and Gmail. As a result, there are a few highly concentrated targets for hackers. Unsurprisingly, hackers focused their efforts on Mt. Gox, eventually stealing more than $460 million.
In a hypothetical world where average people can more securely host their own wallets and email servers (configured slightly differently), I wonder if there'd be sufficient payoffs to incentivize nefarious hackers.