Lucent (AT&T spun them off to commercialize things from Bell Labs) had the absolute best product of the late 90s/early 2000: the Ascend MAX DSLAM/modem bank. Before that, an ISP needed T1 phone lines (24 channels) plugged into a CSU plugged into 24 modems plugged into a chassis that would emit serial that would be plugged into a router, along with a server that would do authentication and logging for billing and IP assignment. The Ascend MAX turned all of that into one box: phone connections to ethernet and all services provided and remotely administrated. Insanely great.
The problem was that Lucent's salespeople were very good, and the market for new ISPs was huge -- everybody was starting one or expanding their available markets -- so Lucent started offering financing.
When you finance your house or car, your loan is backed by the asset: the house or car still has some large percentage of the loan value at any given time, even with depreciation.
When you finance your ISP equipment purchase, Lucent assumed that they could always repo the MAX and sell it at a discount to some other growing ISP.
They didn't count on the ISP market collapsing.
Last time much of the entire market and product was new, e.g. web purchasing was barely in its infancy, companies were building up around that and the web wasn't an integral part of peoples lives, yet. Today, everything we do is around smart devices, the internet etc, so I don't think a collapse like we saw during the dot com boom/bust is likely. But that's just my opinion, could be totally wrong.
My anecdote is the opposite: My father was an engineer at a company that made machines for semiconductor manufacturing.
They had a physical product, customers liked them, they sold each machine at a profit - none of the obvious-with-hindsight folly of companies like Pets.com.
However, when the dot-com bust happened they went out of business anyway. Turns out the collapse of the likes of Pets.com dropped the demand for semiconductors from the point where every wafer manufacturer wanted to expand capacity to the point where no-one wanted to. Boom, no orders. And of course, some investors when they see 'tech stocks' are falling, will sell your stock even if your business is much less speculative than the likes of Pets.com.
There were three lessons I learned:
1. Your business may be nothing like Pets.com and may seem to have strong fundamentals - but if the bottom falls out of tech stocks, you can end up unemployed anyway.
2. When the going gets tough, satellite offices get hit before head office.
3. If you have car/mortgage/credit card payments, you can get insurance that covers the payments if you lose your job. A lot of the time this isn't a good investment - but once the company started laying people off and everyone could see the writing on the wall, people with debt brought gold-plated insurance and were glad they did.