How Pledged Is A Pledged Delegate?

[Patrick Appel] Roger Simon's article about the Clinton campaign's plan to court pledged delegates is enlightening:

Hillary Clinton’s presidential campaign intends to go after delegates whom Barack Obama has already won in the caucuses and primaries if she needs them to win the nomination. [...]

Pledged delegates are not really pledged at all, not even on the first ballot. This has been an open secret in the party for years, but it has never really mattered because there has almost always been a clear victor by the time the convention convened.

But not this time. This time, one candidate may enter the convention leading by just a few pledged delegates, and those delegates may find themselves being promised the sun, moon and stars to switch sides.

“I swear it is not happening now, but as we get closer to the convention, if it is a stalemate, everybody will be going after everybody’s delegates,” a senior Clinton official told me Monday afternoon. “All the rules will be going out the window.”

I don't see how this would be any less controversial than winning the nomination based on the super delegate vote.