Obscurity can definitely be an important part of security, especially from less sophisticated attackers like your crackhead uncle Jimbo who's just looking to get his fix.
But I think everyone who owns bitcoin should assume that some unknown number of entities know they own it and maybe even how much. Might be the IRS. Might be the NSA. Might be Coinbase. Might be a Chinese agency. Might be a sophisticated criminal gang that mines data breaches like Ledger's to try to identify potentially lucrative targets.
There's a few things you can take from this.
  1. Strength in numbers. The more of us there are holding it, the less likely you personally will be targeted. There's likely already millions of us holding coins in our private keys.
  2. Don't stand out. Don't brag and don't flash your wealth publicly, especially online. Not only does this incite envy, but every piece of data you put out that attaches your identity to your wealth increases the number of eyes looking for weakness, or gold diggers hoping to suck you dry.
  3. You don't need to be Fort Knox. You just need to look like more trouble that you're worth. Fake security cameras and security lawn signs without the system to back it up are legitimately effective because predators always prefer the weakest prey.
  4. Monitor and learn from attacks that do happen. Try to decide if you would lose your coins in the same situation and adjust your security model accordingly so long as the increase in complexity isn't overly burdensome.
Do all this and don't stress too much about the fact that many people out there may know you own bitcoin. Key security is partially a numbers game, and a tiny percentage chance of theft isn't worth freaking out about, just studying and constantly adapting to.
Fear is the mind killer, and you need to mind alive if you want to successfully secure yourself and your wealth.