Since I work in the banking industry and have to keep up on all the money laundering, OFAC and other regulatory laws I can speak from experience here.
You cannot be prosecuted for simply taking money out of the bank, period. That's a red herring.
You cannot be prosecuted for routinely taking money out of the bank in amounts under the $10,000 reporting requirement that the bank has to the Fed's either. If you cooperate with the bank, understand why the reporting requirements are there, and tell the bank what the money is being used for you'll not get a visit from the Feds.
You can be prosecuted for routinely taking money out of the bank in amounts designed to be under the $10,000 reporting requirement and refusing to tell the Bank what the money is for. That's called "structuring." The bank has a legal responsibility to report the transactions once a pattern has been established and there is reasonable doubt/suspicion about the bank's customer making the withdrawls, and then lying to the FBI about why the money was withdrawn from the bank.
That is exactly what Denny Hastert was arrested and indicted for.
Prior to the withdrawls in question, Hastert had zero pattern of activity indicating something suspicious was up. It was when he started making large withdrawls, then questioned about those large withdrawls by his bank did he establish a pattern of making withdralws under the $10,000 reporting requirement.
He then refused to tell his bank what the money was being used for which raised further suspicions, forced the bank to report the transactions, after which the Feds were called in. The fact that he lied to the Fed's made it a Federal Crime.
Now, I'll tell you that I don't like these stupid reporting requirements either (most banks don't either..) but it's the law and if we refuse to follow it, the bank is then under investigation for enabling/allowing money laundering and that has very serious consequences to the bank's ability to do business.
The last bank I worked at (ABN AMRO) here in North America was caught up in a money laundering scheme, nailed to the wall by the Fed's (Elliot Spitzer in NY no less...) and as a result that bank no longer exists here in North America.
Structuring withdrawls to avoid the reporting requirement is serious shit and if a bank doesn't report it they go down too.
Makes the 18th century Brits look like pikers...
Suppose you withdraw $500/week from ATMs over the course of a year. Is that suspicious activity?