IMO it all depends upon use. Many of those no contract type plans are either $1/day, or cost some amount per month, month-to-month, but then have no minutes and any time you use minutes, you pay an arm and a leg.
If you really are carrying a cell ONLY for emergencies, and not regular use, it may make sense. But any regular use and I can see getting burned or having a brick until you can refill.
Granted, cellphone service rates for contract use are ridiculous. They are so high, and while some of it seems to subsidize the cost to buy a phone, even after your contract date, or if you bring your own phone into the mix, the rates are not lower. "Competition" has not helped this.
And forget about texting. Most overpriced consumer item on the market...