A video showing Transportation Security Administration officers testing travelers' drinks at a departure gate in Columbus, Ohio, over Labor Day weekend has ignited a new round of condemnation for the oft-criticized agency. The TSA, however, says the policy is nothing new.

The video, posted on YouTube on Monday and featured on NBC Nightly News with Brian Williams Tuesday night, has already garnered almost 125,000 hits and nearly 900 comments from angry travelers. It shows two TSA officers swabbing bottles of water, a carton of coconut water and a cup of coffee, among other liquids.

"Now remember that this is inside the terminal, well beyond the security check and purchased inside the terminal ... just people waiting to get on the plane," YouTube user danno02 says in the video's description. "My wife and son came back from a coffee shop just around the corner, then we were approached. I asked them what they were doing. One of the TSA ladies said that they were checking for explosive chemicals (as we are drinking them)."

The TSA insisted Tuesday that its policy of checking liquids beyond the security gate has been in place for five years now. TSA agents will randomly patrol the gates using a test strip and dropper containing a non-toxic solution, it said.

TSA blogger Bob Burns notes that the issue pops up from time to time, but the policy has remained the same since the summer of 2007.

"The most popular question that comes up with this topic is: 'Isn't this redundant?' On the surface, it does seem that way, and it's the first logical thought that many have. However, any security expert will tell you that nothing is ever 100 percent secure. So, gate screening is kind of like our safety net to keep up with anybody who might be trying to get things past conventional screening," he explained.

Burns said the agency stays away from static security tactics to provide the necessary dose of unpredictability that makes it more difficult for those looking to commit acts of terror.

"If everything we did was always the same, it would provide a checklist for people to know exactly what to expect," he said. "While this would be extremely helpful for passengers, it would also be useful to those wishing to do us harm."

In other words: TSA believes unpredictability is the best key to maintaining security.

Liquid testing inside the terminal is simply another outcrop of the policies put in place after authorities thwarted a transatlantic terrorist plot involving liquids in 2006. The more familiar result of that case is the "3-1-1" rule, whereby passengers may carry one quart-size clear plastic bag containing liquids or gel up to 3.4 ounces.

As a result, many thirsty fliers purchase beverages inside the gate. Those too, it seems, are not exempt from the eyes of the TSA.