I would say that 8GB is just fine and should be plenty for any/all uses. I recently helped a graphic designer friend purchase a new laptop, and he only utilizes 4GB in photoshop editing the biggest picture with the most layers he has. He only had photoshop open though, if you're one of those people that likes having a bunch of programs and 30+ tabs of your favorite internet browser open, you may need more than 8GB.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 120 GB Vertex 3 Max IOPS, 2 TB Samsung EcoGreen F4, 8GB 1600MHz G.Skill @1.25V, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Hand-Built Wood Case