I can't speak for everyone, but while I'm a little saddened by this, I'm too busy being optimistic about the future to get worried about anti-trust. NatSemi makes good chips, but everything else seemed a little shaky (have you seen some of their newer datasheets...?) and I hope being owned by TI will help a lot of these things.
The market's diverse enough so it's not likely to be an issue. TI and National don't have a corner on any part of the market that I'm aware of. There's plenty of competition from the likes of Analog Devices, Maxim, Freescale, Siemens (not sure if Siemens is still in the IC market, tho) etc...
TI is definitely the largest player. Why shouldn't market consolidation by TI be questioned?
Diversity may also be misperceived, as the companies may not compete directly on all product lines. If you need a chip for something, there are times when it is only produced by one company.
Here are a few quickly-Googled numbers:
TI
Revenue: $13.966 billion
Net Income: $3.228 billion
ST Microelectronics
Revenue: $8.465 billion
Net Income: $1.131 billion
NXP Semiconductors
Revenue: $5.44 billion
Net Income: $1.823 billion
Infineon (Siemens)
Revenue:$4.688 billion
Net Income: $937 million
Freescale
Revenue: $4.46 billion
Net Income: $1.15 billion
Analog Devices
Revenue: $2.8 billion
Net Income: $712 million
ON Semiconductor
Revenue: $2.131 billion
Net income: $395.8 million
Maxim
Revenue: $1.998 billion
Net Income: $129 million
Fairchild Semiconductor
Revenue: $1.6 billion
Net Income: $193 million
National Semiconductor
Revenue: $1.42 billion
Net Income: $209.2 million
Linear Technology Corp.
Revenue: $1.17 billion
Net income: $361 million
The US used to have a consistent anti-trust tradition. With Ma Bell reuniting and mergers like this, it seems to be waning.