Unless you're plugging into a two-prong outlet, the case will be grounded to your room anyway. Which means essentially, your case is part of the carpet.
San Francisco: Gigabyte GA-Z77X-D3H | Intel i5-3570k @ 4.5ghz | 16 GB DDR3 @ 1866 | Gigabyte WF3 7950 @ 1125/1500
Honolulu: Gigabyte MA790X-UD4P | AMD Phenom II X4 955 @ 3.8ghz | 8GB DDR2 800 | Sapphire HD4890
London: ASRock 4CoreDual-VSTA | Intel Dual Core E7400 @ 3.1ghz | 2GB DDR2 667 | ATi X850 XT @ 540/590