Bank accounts are't for storing your retirement savings. Even with the current low rates you can get 3% from 20 year Treasuries. If you want more yield you'll have to take some risk, which is why diversified portfolios are always advised.
In other words you must take the risk of forgoing retirement when trying to beat inflation. In 2008 pretty much the only diversified portfolios that didn't take a huge hit were the baskets of low-risk investments.