“They can simply seize it on probable cause and in many cases that have nothing to do with drugs.”
The gov hates cash, because cash refuses to produce data that can be collected by the NSA. That’s why they’ll soon will force you to use electronic banking, credit- or debit cards only. So total surveillance can be guaranteed.
Just like france and italy already did. They prohibited cash transactions above 1000 by law. http://www.forbes.com/sites/jonmatonis/2013/02/14/france-plans-to-prohibit-cash-payments-over-e1000/
It’s only a matter of time for these laws to show up in the US.