What is a negotiable bearer bond? If I stole $600 Million worth of them, could I just go redeem them at the corner bank? What do you do with them? Would there be some way of tracing them through serial numbers so that it would be hard to do anything with them?
Diver
A bearer bond is the “ancient” type of bonds, rarely issued today. The idea was, someone would buy a bond in the market(let’s say for $1000), and it would be mailed to him physically. On the bond were “coupons” that had dates on them, which could be clipped off and deposited in a bank on the dates listed. These were the semi-annual interest payments. When the bond matured, you would take the actual bond (and any coupons you forgot to deposit) to the bank and get your $1000.
The problem with bearer bonds is the security risk. Anyone with that coupon gets the money. As far as I remember, there were no serial numbers “back in the good old days.” Today, most bonds are book-entry style, which means a transfer agent with a computer has a list of who owns the bonds, and the interest payments are automatically dropped into your brokerage account.
Just finish watching Die Hard again?
As seth mentioned, Bearer bonds are not recorded as to the owner, those are Registered bonds, which make up the vast majority of corporate bond issues. In the United States, corporate bearer bonds are rare, but they are more common in Europe. Municipal Bonds were often issued as Bearer bonds prior to 1983, but since then have been in Registered form. However, you can still find some long term Bearer bonds availible in the marketplace.
One use I’ve heard of for bearer bonds is as a way to earn interest on all that cash you’re stuffing into your mattress.
In other words, if you want to have a lot of money hidden in your residence (or where-ever) for whatever reason, one way to do it is to stuff your mattress with cash. But this won’t earn interest. So instead, you might use bearer bonds, and keep them with your guns, ammo, and cigarettes for barter when the great breakdown comes 
By the way, I think that bearer bonds, by their very nature, are negotiable instruments. Thus, the phrase “negotiable bearer bond” would seem redundant.
"f I stole $600 Million worth of them, could I just go redeem
them at the corner bank? "
Sure, but you would have a visit from the FBI & the tax people shortly.
There have been no new bearer bonds issued in the U.S. since 1982. (There are still legal bearer bonds out there that were issued before that, but they are becoming rare as they are redeemed.) Issuing new ones was made illegal because they facilitate tax evasion and money laundering. As of about five years ago, it was still legal to issue bearer bonds in many European countries, but the U.S. was putting pressure on those countries to stop the practice. I have a vague recollection of reading that it is illegal for U.S. citizens to buy bearer bonds in Europe, but I could be wrong.