I was a young-ish dev at a smallish (200 or so people) company in the Bay Area during the dot-com crash. I came in one day to find that something like 1/3 of the people in the company, seemingly chosen at random, no longer worked there. Those of us who remained were consolidated into one floor instead of the two we had before. My salary and options were not affected, and the (basic by modern standards) free food stayed pretty much the same, though I think WebVan was no longer around to deliver it. I left soon after that, and the company lived on in cockroach mode for years. I think it was eventually acquired, but I haven't paid much attention.

One reason my experience wasn't catastrophic was that I was at an infrastructure company, not a hype-driven one like Pets.com. If/when the current ad bubble bursts, average devs will fare best working at companies several steps removed from the hype. People may not want micro-targeted ads, but they'll still need software.