The fact that someone can beat a key out of you is not what is usually meant by 'brute forcing' a key, in a cryptographic context.
The only feasible thing against AES 128 right now would be if a flaw was discovered. This is also why it doesn't matter whether you use 128, 192, 256, or higher. If one is flawed, they all are. The reason we even have higher than 128 is simply because the government loves excessive amounts of redundancy. It lets them sleep easier at night, even if it's completely unnecessary.
Competitions are held in which anyone can submit their own algorithm as a possible contender. Like a beauty pageant, the entries are narrowed down over a few rounds until just a few are left. Eventually, one algorithm is chosen and declared the winner!
The whole process is done in the open and, similar to RFCs, anyone who wishes to may provide feedback.
The SHA-3 competition took roughly five years. You can read about the whole process on the NIST's web site:
http://csrc.nist.gov/groups/ST/hash/sha-3/index.html
Numbers about total world computing power (most of it probably stuck in GPUs doing windows animations and playing Call of Duty) bandied about are in the Ne18ish ops/sec range, age of the universe is in the 4e17 range.
And I have a great deal of margin by treating a 'decrypt and verify' operation as a 'basic operation' and using a completely preposterous time period like the age of the universe instead of say, 10,000 years. Nobody is brute-forcing 128 bit keys anytime soon, that's a pretty basic mathematical and physical given. But if you're particularly paranoid, you can just as easily use 256 bit keys - nobody is brute-forcing those until we hit the singularity and become a galaxy-encompassing brain. Even then it might give us a serious, millennia-long headache.