From a strategy perspective, it matters hugely to anybody in or thinking of launching a startup.
If there's no bubble, then the current happy days are likely to continue: lots of money chasing after good ideas, huge rewards for the winners and so as a result easy access to angel investments and high valuations. Yay! So it makes sense to think of a strategy focused raising a lot of money on great terms.
On the other hand, if there is a bubble, a very different strategy is called for. One option is to sneak in and raise money at bubbleicious valuations before it pops. But that risks setting expectations with investors that will be impossible to meet in a post-bubble environment -- a recipe for a rocky medium term. Another option is to batten down the hatches and focus on getting to cash-flow positive ASAP to leave yourself in the best position to pick up the pieces as other unsustainable companies crumble. Or as I said elsewhere in the thread, maybe it's a good time to be contrarian: work out where the bubble is likely to be, and position yourself differently so that when it pops you can be there as one of the first exciting post-bubble companies. And it's also possible to take a straddling strategy, ready to go either way depending on whether or not it's a bubble.
Of course it's impossible to know for sure what the answer is. But hearing and understanding various perspectives (right and wrong) and others' reaction to them really helps map out the strategy space and highlight the best places to be.
I think the fact that you listed so many options tells the real story: all this thinking about whether there is a bubble is a distraction for entrepreneurs (to a first order approximation). Build a great product that people will pay for - there's money for those no matter the state of 'the bubble'.
I see it differently. A good startup has multiple options about what great products it can try to build, the cost and revenue models behind them, and its funding strategy. Products that are great for people who are throwing around money in a frothy bubble environment can be millsontes in a buttoned-down, post-crash situation. So while too much reading thinking about the overall context is a distraction, ignoring it hugely increases risk and misses opportunities for significant advantages.
There is a strange and powerful drive to be the first person to declare that something has jumped the shark. I don't know exactly what it is about the Internet that has done this, but the time it takes for someone to leap up and declare that something is "over" just keeps going down, to the point that it has now reached somewhat absurd levels. Maybe we're in a bubble, maybe not, but either way the declaration seems to be getting made on awfully scanty evidence... but it's important to be first.
Of course on a long enough time scale a bubble in tech is inevitable almost no matter how you slice it.
I think that it isn't necessarily to be the first to declare it, but people want too see it coming. Where the first tech bubble surprised a lot of people and they lost money. If you know your going to lose some, it doesn't hurt as bad. Kind of like playing roulette. You expect to lose but it feels good when you win.
Why is this topic so damn fascinating to people?