TS described EXACTLY what I went through. After googling I thought it was normal too. Truth is, If the problem persists Ur not sure, do call up a proper electrician to check the wiring.
My case
1. Thought it was "just static/normal" on the MBP, changed to the 3 pin with proper ground=solved.
2. Checked other stuff sometimes usb also got some buzz. Thought it was just THAT outlet. Installed those Belkin multi socket adapters n the red light (on the adaptor itself) lighted up telling me some wiring got prob.
3. Sometimes microwave (different wall plug) also buzzing...
(after nothing happening for a while n using rubber flip flops in the house)
4. Got new iPad, same buzzing feeling still...
What actually happened was the grounding for the whole house gone kaput alredy, so had to redo the whole thing (it's a 30 year old house). After that no more static/buzz whatever

. Lucky me. So my one advice, if it annoys you, nothing wrong to get Ur wiring checked, u could b saving Ur equipment's lifespan (n yours too). Don't play play with electricity oooooo....
NOTE: don't freak out though, might not be the exact same case for everyone, just sharing my experience n solution
This post has been edited by krazee_k: Jun 11 2012, 08:50 AM