Or maybe more properly, the dangers of flying with a cupcake - one that is coated with lots of frosting.
The popular media has has a number of reports (1, 2, 3) of how "heavy handed" Transportation Security Agents (TSA) confiscated a women's cupcake as she attempted to pass through security with it. The frosting was considered by the TSA agent as a "gel", a restricted material, and the amount of frosting was judged to be in excess of the amount allowed on a plane in the US.
Although it certainly is fun to take potshots at the TSA and joke about how the agent was hungry and just wanted the cupcake for him or herself [*], rheologically speaking, the TSA was right on this one. Frosting is not a polymeric gel, but more of a "colloidal" gel with plenty of non-Newtonian behavior - certainly yield stress, but also likely shear thinning, and maybe even some thixotropy (I haven't measured the properties myself. If any readers have, feel free to add what you know in the comments box below.) And as the TSA commented regarding the incident, malevolent people are more likely to disguise their means as ordinary object and not give them a distinctive "explosive" appearance:
Unfortunately, this incident has come out as yet another example of a sweet innocent person vs. the evil TSA. While in many cases I do agree with that viewpoint, this is one where I clearly agree with the TSA.
[*] I can't imagine any agent eating anything that is confiscated from passengers. Would you really risk your health/life by eating something from an stranger? We're not talking about a box of donuts that's sitting in the breakroom.