The question is whether, when and how bad it will burst.
Predicting market events like bursts is extremely hard, even for experts - so hard you can make a lot of money from it - remember that economists too said that the housing market was a bubble and wrote posts to mock how, for four years people kept repeating the claims.
If billion dollar valuations for buttons that text 'Yo' isn't a speculation bubble on the one area of US industrial growth, an area that gets a lot of cash influx to keep it going (much of it taxpayer), I don't know what we could call a bubble.
Not all bubbles burst. But how much confidence do you have that the market will remain the way it is today after another series of Snowden revelations, a housing crises (or water crisis) in the Valley, the release of financial information that makes people lose faith, a shocking event like Alibaba beating out Amazon or something, etc?
If you think something like that could seriously damage the industry then you have to admit that the demand for the good and services is highly elastic - or at least fragile.
Fragility of a market + overvaluation and overspeculation implies a bubble.