Most of them operate a high profile, commerce-based web site. Very typically, the shares double on the first day of trading on the back of enormous trading volume. By virtue of the amount of turnover these shares experience, it's clear that the owners of these shares are speculators, not investors. Shares are being bought, and then dumped a couple of days later. Before there was an Internet, this current mania played itself out under different names.
Speculative mania goes back as far as time.
Past manias existed around the issuance of shares in the South Sea trading company, railroad stocks in the U.S. in the 1800s, and most recently, biotechnology companies in the early 1980's. Every one of these has ended the same way. Prices eventually collapse as the hype fades and reality sets in. In a mania, the valuation of a company is ignored. Stock prices do not reflect any fundamental economic basis.