"Men did not love Rome because she was great. She was great because they had loved her." -- G.K. Chesterton
"When Faith preaches Hate, Blessed are the Doubters." - Amin Maalouf
This is being blown out of proportion. The knifes they are allowing are not much of a threat.
The concerns with wheel chairs is most are made of hollow metal tubes in which both explosives and parts to make a firearm can be hidden. That also is the reason they want laptops separate for careful examination. It would not take much of an explosion to bring down a jetliner. If I remember correctly, they initially required people to turn on electronics to make sure they were real - but booting time was probably too delaying.
I love the NSA. It's like having a secret fan-base you will never see, but they're there, watching everything you write and it makes me feel all warm and fuzzy inside knowing that I may be some person's only form of unconstitutional entertainment one night.