I have
this netbook and I use Photoshop with no problems, so maybe it depends on which one you choose.
That's the "standard" netbook specs, my Toshiba NB-205 is the same (1.6GHz processor, 1G RAM, plenty of hard disk space). The Adobe page linked to shows two things netbooks don't meet: 1024x768 screen (netbooks are 1024x600, that's about an inch smaller in the vertical than "required), and DVD drive (but if you REALLY need that, you can PLUG IN an external DVD drive into a USB port).
No, netbooks are not powerful enough and the screen is too small. Get a MacBook. PS suites are perfect fit for it, and it's light and small and spiffy. And hassle free.
Worst case, netbooks (well, mine anyway, I presume others too) have a VGA connector to plug in an external monitor that you can run at higher resolution. When I use my netbook in the office (it's where I have it plugged n to recarge anyway) I use it with a 21" CRT set at 1400x1050. It'll run the monitor at 1600x1200, but only at 60Hz refresh, and I can see that flashing and it about give me fits, but 1400x1050 at 75Hz looks good.
You may well be happier running Adobe Bloatware (woops, did I just say that?) on a larger-screen, more expensive laptop with a faster processor and more RAM, but technically and apparently practically it CAN run on a netbook.
I don't have the latest and greatest of every software package on my netbook (except for Firefox), but it hasn't had a problem running anything I've loaded and run on it.