The following is not legal advice, I do not represent you.
As a formal federal prosecutor, I can tell you that you should be really careful in this area. As noted above, Suspicious Activity Reports get generated when you make cash or cash-equivelent transactions ranging from $3000-$10,000. These reports go to various law-enforcement types who investigate them to varying degrees.
Generally they are looking for money laundering and structuring.
Money laundering (
http://www.law.cornell.edu/uscode/text/18/1956) basically involves monetary transactions in which the money was obtained illegally and you know it was obtained illegally and you are making the transaction in an attempt to further the illegal activity or conceal the source, nature, etc. of the funds.
Structuring (
http://www.law.cornell.edu/uscode/text/31/5324) involves making monetary transactions in an attempt to circumvent reporting requirements. The basic reporting requirement kicks in when moving more than $10,000 in cash in a day. Note that a report will be generated even if you do smaller transactions at multiple branches of a bank in one day that aggregate to over $10,000. The money in this case does not need to be from illegal conduct. The only requirement is that you are structuring transactions in order to avoid the reporting of the transactions.
If you are ever approached by law enforcement asking about transfers you made my Practical, Non-Legal, advice is to tell them unequivocally that you want to speak with a lawyer before answering any questions. The easiest way to prove your intent in structuring transactions was to avoid reporting requirements is for you to tell them that. Otherwise it is very difficult, although not impossible, to prove.
It is also generally a bad idea to go telling people on the Internet that you are structuring your transactions so that they are not reported. You would be surprised at how easily law enforcement can tie you to an account on a website.
If you ever take $10,000+ in cash on a flight, my further Practical, Non-Legal advice is to make sure you report it on the Customs form that asks you that question. It is not generally illegal to carry large amounts of money. However, if you lie on the form and they find out they WILL seize all of your money, and they may arrest you, and they could charge you with a federal crime.
Ike
The preceding is not legal advice, I do not represent you.