Public employee unions get a bad rap, says Anne Wass, president of the Massachusetts Teachers' Association.

They're accused of being unrealistic and greedy. They're blamed for pushing property tax overrides that critics say are promoted on behalf of schoolchildren, but wind up paying for inflated teacher salaries. Their political power is hinted at darkly when Beacon Hill fails to pass legislation the unions oppose.

But Wass thinks such criticism fails to compare local government employees to private sector workers.

"You hear about greedy teachers," she said, but "if they say the benefits are so great, look at what someone comes out of college with and gets as a teaching salary, compared to their fellow graduates, (or) the bonuses people in business get. The list goes and on."

But Steve Poftak of the Pioneer Institute said citizens won't support greater spending on government unless they see more accountability there. "I'm all for paying good teachers more, but when it's just that blanket (policy where) everyone, lockstep, gets a raise in good times and bad, I think it does encourage a certain amount of cynicism."

Michael Widmer, president of the Massachusetts Taxpayers Foundation, said the problem is that towns can no longer afford the salaries and benefits that unions have won in the past.

"I don't blame them for negotiating hard for their members," he said. "But what's happened is that we have a set of benefits for public employees at the local level - and in some other areas as well, like the MBTA - that is absolutely not sustainable."

Widmer added, "You can't ask people to support additional taxes to pay for services when you have these kinds of benefit levels, particularly for health care, that are just way out of line with what's common today."

Those benefits include health care for both current and retired workers, as well as pensions. The advocacy group Citizens for Limited Taxation declares the looming cost of providing benefits for future retirees to be "a ticking time bomb."

As of 2006, Attleboro had an unfunded liability of $39.3 million for employee pensions, according to the city's annual financing report. That amount was only 62.7 percent of what the city owes down the line, but it is up from the mid-1980s, when the city had only saved enough money to pay for about 30 percent of its future pension costs.

The story is similar elsewhere. The Bristol County pension fund in 2006 had an unfunded liability of $135 million, or 38 percent of future pension costs. North Attleboro has managed to reduce its unfunded liability to 17 percent of future costs.

Still, Poftak said more cities and towns should join a state program that allows them to fold their pension funds into the state investment plan.

"There's almost no reason for these local pension funds to concern themselves with asset management," he said. "Almost no community has outperformed the state pension fund."

But, as a recent paper for the Federal Reserve Bank of Boston noted, most cities and towns have not even begun to grapple with the future cost of providing health care for retirees. A federal regulation issued in 2004 will require them to calculate that total in the next few years, and Fitch Ratings, a credit rating agency, calculates that most will need to begin saving "anywhere from two to 10 times the current pay-as-you-go amount" put toward retiree health care - taking another chunk out of local budgets.

The unions are "acutely aware of the problem," Norton Town Manager James Purcell said, and have made some attempts to be flexible.

Poftak argues that's because they may see the writing on the wall.

"I think some farsighted unions have taken the long view on this," and want to do what they can to keep good benefits for their workers without bankrupting municipal finances, he said.