One big bubble ready to burst.
An iBubble.
Right.... because the valuation of AAPL is completely based on speculation rather than revenue, earnings and assets. "Bubbles" are defined as
trade in high volumes at prices that are considerably at variance with intrinsic values
(see Wikipedia for multiple references on that definition).
If anything, AAPL has been the anti-bubble for years now. The P/E ratio of speculative stocks like Amazon (AMZN) is over 290. The P/E ratio for AAPL has been hovering at 14 to 16 all year (currently 15.6). The P/E ratio is even lower for AAPL if you calculate the forward P/E (i.e.: price to earnings using this year's earnings). It gets even more insane if you look at the fact that Apple has one fifth of the market capitalization in no-risk cash or cash-equivalent assets and the company has zero debt. If you subtract the cash assets from the market cap and then recalculate the P/E it falls well below 10. For reference, Google's (GOOG) P/E ratio is 20 and Microsoft's (MSFT) is about 15.4. So investors are being more speculative on GOOG and just as speculative on MSFT, despite AAPL outperforming both companies consistently quarter after quarter.
If you want an example of a "bubble", then look at Amazon (AMZN). With their 290+ P/E ratio, investors would have to see Amazon garner near 100% of all retailing (not just online retailing) in the next 10 years without drawing government regulation because of monopoly power on price controls. AMZN is the the definition of a "bubble" stock. There are no fundamental "intrinsic values" to support Amazon's stock price -- it is 100% speculation that something about Amazon's formula will one day yield Apple-like profit. On the other hand, Apple is doing "Apple-like" profit today with potential to grow in the markets they profit in considering their current share of the market and their opening up to new geographies internationally.
There's a little education in economics for you. Bubbles are about things being artificially inflated due to speculation driving demand. Nothing about AAPL stock price is speculative. If the company maintained its anemic P/E ratio and just kept increasing revenue on their current (or half their current) trajectory the stock price would break $1000 in the next 12 months.