One difference between a bubble and a declining market segment is that the bubble bursts -- abruptly.

So it doesn't matter whether people repeat prophecies or doom for a long time or not -- unless it's actually a bubble, it won't ever burst. At worse it will start declining slowly.

That's why the arguments like "it hasn't burst all those years so it's not a bubble" don't get it either.

Being a bubble is not something that has to do with duration (whether it lasts for a long time or not) -- it has to do with the non-linear effects of the burst.

Of course it the burst never comes, or it's instead some gradual decline, then it's not a bubble.