I am just jumping into this for fun to play devil's advocate. "Trivial" is probably the wrong word to use, but I can see it being "trivial in some situations vs. how hard people imagine it might be".

If I were to file a lawsuit against you as an individual, or prosecute you as a government agency, then probably yes I could. First, I can probably simply compel you declare them during discovery. I will allege that you're engaging in fraud and money laundering as part of shielding your assets against a debt that you owe me (let's say). I will explain that you've purchased bitcoins on an exchange for the purpose of shielding and hiding your wealth. (You're declaring bankruptcy in order to get out of a debt.)

We'll discover how much you've transferred to the exchanges that you do business with by compelling you to declare it, or by subpoena. You're now in the position of proving what happened to that money, where it went, and demonstrating that it's not still an asset. Enough people have heard about bitcoin and Silk Road on the news that there's a good chance a judge will see this as shady behavior, especially if you're not cooperative in revealing information.

If you have purchased bitcoin mining hardware and mined the blocks yourself, then we'll probably find that out during deposition. I'll figure out how much hardware you have and what its estimated hashrate is. You can keep the actual bitcoin addresses secret from me, but the fact of the wealth created by them will not be secret from a court, and you'll have a steep hill to climb to keep the bitcoin addresses and the amounts you've earned secret without contempt of court. If you've transmitted nontrivial amounts of money that's obviously going to a bitcoin exchange, or left any trail of financial records of purchases of bitcoin mining hardware, or if you disclose by answering honestly during deposition, and refuse to explain what's happened to those coins, then it will be obvious to a court that you're engaged in black market activity, money laundering, or are shielding your assets. An honest citizen doesn't hide their bank account information and activity from a court in circumstances where it's relevant.

If you have left no connection whatsoever between your traditional identities like your bank accounts, and with your bitcoin identities (like through an exchange), then it will be harder, especially if you lie under oath and claim you don't have any. For example: maybe you got into bitcoin in the early days when you could mine on a PC. You held onto those coins for years and are now a bitcoin millionaire. You recently bought mining hardware in a server farm you've never seen with those coins anonymously, and you're now mining more coins. This you could probably keep secret. If there's been any conversion with USD without a lot of anonymity, then there's going to be an obvious trail that will show up in a civil or criminal investigation.

Now, to be fair, I cannot find this information out about you, you being an anonymous person I know nothing about over the Internet. However, I also have no cause to care. If I have any cause to care, like if we have business dealings, then I will have enough information to leverage this process against you. Furthermore, it's not like I can find out your bank account number or credit card number either. The point I'm making from this is that bitcoin is not more anonymous than those instruments unless you've gone really far down the opsec road, buying mining hardware in cash, and engaging in money laundering to keep these secrets, lying under oath, etc. But to be fair that is an advantage. If you buy bitcoins in cash, you can spend them online anonymously. I would not describe any of this as "trivial" necessarily, but at the same time, I also feel like if you and I were to get into any legal altercation involving finances and money, I could probably do it. Though you do retain the power to keep them secret by risking contempt of court.