As bubbles expand and hot money starts burning holes in corporate pockets, merger and acquisition deal terms begin to leave reality behind. Often one deal of such breathtaking size, scope and hubris is struck that — in retrospect — heralds the end of the era.

The junk bond bubble of the 1980’s, for instance, hit its apex with the December 1988 leveraged buyout of processed food conglomerate RJR Nabisco, which featured a prolonged bidding war by a Who’s Who of the corporate raider/LBO community. At $25 billion, it was seen as RJR Nabisco at the time.

It was also the end of the bubble. In 1989 junk bonds began to default, junk powerhouse Drexel Burnham Lambert collapsed and its “junk bond king” CEO Michael Milken was imprisoned. In the recession that followed most of the bubble’s big players either retired in disgrace or found other ways to make money.

During the late 1990’s dot.com bubble everyone became convinced that “new economy” companies (i.e., those related to the Internet) were orders of magnitude cooler and more valuable than old economy companies that made and managed physical things. The media variant of this idea held that content carried online was by definition better than that which was delivered via TV, radio or the printed page. America Online was the pioneer in digital media, and therefore preternaturally valuable. So it decided to use its “supermoney” shares to buy the old-school content of Time Warner for an astounding (even by today’s standards) $182 billion.

The timing couldn’t have been worse (or more on-point for this discussion). Within a couple of months the dot-com bubble burst, sending AOL stock down by a quick 70 or so percent. The NASDAQ, home to most of the previous decade’s tech icons, eventually fell by 80% (a huge drop for a stock index) and didn’t recover for another 15 years.

The 2000’s didn’t have a single monster deal that defined its peak. But they made up for it with sheer quantity. The following chart shows 2007’s aggregate global M&A activity exceeding the 2000 peak comfortably — and then plunging by about two-thirds in 2009 as the banking system that had financed all those delusional deals nearly died.