In the beginning, laundering money was a physical effort. The art of concealing the existence, the illegal source, or illegal application of income, and then disguising that income to make it appear legitimate required that the launderer have the means to physically transport the hard cash. The trick was, and still is, to avoid attracting unwanted attention, thus alerting the Internal Revenue Service (IRS) and other government agencies  involved in searching out ill-gotten gains.
In what could be described as the "lo-tech" world of money laundering, the process of cleaning "dirty money" was limited by the creative ability to manipulate the physical world. Other than flying cash out of one country and depositing it in a foreign bank with less stringent banking laws, bribing a bank teller, or discretely purchasing real or personal property, the classic approach was for a "smurf" to deposit cash at a bank. Essentially, platoons of couriers assaulted the lobbies of banks throughout the United States with deposits under the $10,000 reporting limit as required under the Bank Secrecy Act. The result was the formation of a serious loophole under the Bank Secrecy Act, allowing couriers almost limitless variables in depositing dirty money such as the number of banks, the number of branch offices, the number of teller stations at one branch office, the number of instruments purchased, the number of accounts at each bank, and the number of persons depositing the money.
In 1986, the Money Laundering Control Act (the Act) attempted to close the loopholes in the prior law that allowed for the structuring of transactions to flourish. In criminalizing the structuring of transactions to avoid reporting requirements, Congress attempted to "hit criminals right where they bruise: in the pocketbook."
Under the Act, the filing of a currency transaction report (CTR) is required even if a bank employee "has knowledge" of any attempted structuring. Thus, it appeared as if the ability to launder the profits from illegal activity would be severely hampered.
As the physical world of money laundering began to erode, the tendency to use electronic transfers to avoid detection gained a loyal following. Electronic transfers of funds are known as wire transfers. Wire transfer systems allow criminal organizations, as well as legitimate businesses and individual banking customers, to enjoy a swift and nearly risk free conduit for moving money between countries. Considering that an estimated 700,000 wire transfers occur daily in the United States, moving well over $2 trillion, illicit wire transfers are easily hidden. Federal agencies estimate that as much as $300 billion is laundered annually, worldwide. As the mountain of stored, computerized information regarding these transfers reaches for the virtual stars above, the ability to successfully launder increases as the workload of investigators increases.
Although wire transfers currently provide only limited information regarding the parties involved, the growing trend is for greater detail to be recorded. If the privacy of wire transfers is compromised, due to burdensomely detailed record keeping regulations, electronic surveillance of transfers, or other potentially invasionary tactics, then the leap from the physical to the virtual world will be nearly complete. If laundering is to survive it must expand its approach, entering the world of cyberspace.
While change is often a frighteningly awkward experience, for an enterprising criminal operation, that wishes to remain open for business, it is a necessity. As the above mentioned race through laundering history demonstrates, creativity, and not necessarily greed, has been the launderer's salvation. The recent explosion of Internet access,may be the new type of detergent which allows for cleaner laundry.

Reference:
http://osaka.law.miami.edu/~froomkin/seminar/papers/bortner.htm