https://www.wired.com/2013/12/fbi_wallet/The FBI seized 144,000 bitcoins, which are worth $300 million today.
Right now bitcoin taxation is impossible,with or without address blacklists.
It's not impossible. They can raid your home, seize your computer, transfer your bitcoins from your wallet to theirs and then go on a nice vacation with your money.
Yea. How could they know how many wallets you have and how much you have in the first place? Don't use wallet services where they hold your private keys for you.
Also, blacklisting wallets is a very very bad idea. Let people decide on how they want to hold their cryptocurrencies.