Some measures suggest the current bubble is even bigger than the one in 1999. Or at least more broadly carried, in the sense that in 1999 the bubble was limited to a fairly narrow range of tech stocks.
This time it's all over the place. It's not limited to a few stocks. It's not even limited to the broader stock market or to subprime credit. Today even government bonds are in a very special place.
PS: it's also very interesting that so many people here in these comments think that shaving a penny off on order flow is all there is to say about HFT.
And the comments also make me wonder about the staggering popularity of ETFs. ETFs are much bigger than in 2007. In themselves a sound idea, I do wonder how things like the 3x Inverse Synthetic Foobar ETF consisting of 99% bond meat with 1% mystery spices will fare during a real panic.