@Mac266
this is 2 fold.
1) Seagate is not claiming the first 2TB 2.5" drive. As you mentioned Samsung has a drive, and (while rare) we have had 2.5" 2TB SSDs for a few years now. The important bit is that this is a HDD (much cheaper than SSD), and that it is a slim drive which can be used in smaller devices like x86 tablets and ultrabooks.
2) When was the last time that Sammy made a mainstream drive that anyone purchased? Samsung makes some great products on occasion in huge volume, but their HDD business is not exactly large. Having Seagate announce a drive means that you will actually be able to purchase them and find them in stock outside of a few specialty stores.
This is pretty big news. Especially with SSDs dropping in price and starting to eat up the smaller drive segments. A friend of mine just purchased a 256GB SSD for $65 on sale. A $65 256GB SSD, or a $50 250GB laptop HDD... that price gap is getting awful close, and the SSD will blow the HDD out of the water for performance and durability (speaking of physical durability in a laptop... not read/write).