Hard Drive memory. The low end market offers 8 gigabyte memory which is not enough.You can always add a chip with 4 , 8 or 16 giga extra memory, however if you want to download and use programs like Skype, Adobe Reader, Open Office etc. you may know that to run these programs they must be in the "Program files" of your netbook, and the "Program Files" cant'd be removed to the external memory.
The software which comes along with your netbook, will probably use about 7,2 gigs, therefore you are left with less than one gigabyte memory, and the minimum requirement to run applications is 200 MB of free memory on your HD.
I use a netbook for the past six months and it is great.