I guess most folk on here must have heard about the terrible flooding in Thailand.
This has a serious impact on HDD supplies as Thailand is the second largest manufacturer of HDD's.
http://www.reuters.com/article/2011/10/28/us-thai-floods-drives-idUSTRE79R66220111028
If you are thinking of building or even upgrading your present server then expect huge price increase, I bought a 2TB Samsung back in the summer for £57 all in, now the same drive is around the £130 mark plus shipping.
Andy