Court papers recently filed in conjunction with the indictment of Albert Gonzalez reveal that SQL Injection attacks were behind the data breach that allowed hackers to steal massive amounts of data from Heartland Payment Systems, TJX, and other businesses. Over 130 million credit and debit card numbers were ultimately obtained, all because of the failure in a web application to properly validate user-supplied data. The level of knowledge required to enact such devastating attacks continues to plummet, and the criminal desire behind them continues to rise. It's amazing what could have been prevented with proper application security in place.

This attack also perfectly illustrates how exploitation techniques have changed in just the past few past years. Once upon a time, hackers were content to steal the data from a database and then leave. Now, they infect the system with malicious software and perpetuate attacks across a much larger time frame, exponentially escalating the damage. The harm that can come from one relatively simple exploitable hole is phenomenal. Keeping your web applications secure has never been more important.  

http://www.networkworld.com/news/2009/082409-us-says-sql-injection-caused.html