In the case of Internet Bubble 1.0, you had such a huge buildup (and stage set for a huge burst) because you had three forces working in tandem and reinforcing each other:
1) Big banks underwriting IPOs on questionable businesses with unproven models and no revenue expectations.
2) VCs and/or angels rushing to fund pretty much any idea, no matter how sketchy, because of the above.
3) An influx of would-be founders (especially nontechnical founders) and speculators basically gold-rushing out to the Bay Area to try to get something off the ground -- often driven primarily, if not solely, by a lottery ticket mentality, and not by love of their product or business model.
Whether we're currently in a bubble largely depends on your belief in the solidity, or lack thereof, of the companies being funded. Amount of funding, frequency of funding, etc., are only aspects of a bubble -- but they are not sufficient to describe a bubble. It's only a bubble if the investment has reached a point of irrationality, and the only way to determine irrationality is to examine the companies themselves against the investment they've received.
If the shoe fits....
but to the extent people are in denial, drawing this kind of analogy is very definitely doing a service
Well it is. It is hurting the egos of many people here as many are involved in startups. Accepting the fact that it might be a bubble would mean somehow joining the ranks of the hated housing market speculators and bankers.
I am not saying whether it is a bubble or not. But if you see a large rationalization effort into making this "not a bubble" that might be a plausable explanation.