Robert Brokamp is arguing at Fool that people may consider Roth IRA as a place for emergency fund. I totally agree. One should always make full contribution to Roth IRA as long as he/she can still have month-to-month cash liquidity after the contribution.
People may argue IRA should be for retirement purposes but I will suggest we see IRA just as a financial tool. With the flexibility of Roth IRA one may withdraw the entire contributions any time without penalty. With Roth IRA one can still invest in a full spectrum of options: money market, CD, mutual funds, stocks, bonds, etc. Of course people should understand risks vary among different investment options, but it has nothing to do with Roth IRA: Roth IRA is a platform; Roth IRA is not an investment option by itself and thus is risk-neutral.