A can of worms is a can you do not wish to open, especially if you are obliged to eat the contents.

Thus to 'open a can of worms' is to invite pain and detailed unpleasantness. Usually used to avoid doing something.

As in: '''It is possible do it with EnterpriseJavaBeans, but that would be opening a whole new can of worms.'''

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The way I first heard this expression had nothing to do with eating the contents(!); rather, the essential element was that once a can of worms is open, the worms squiggle about and getting them all back in to the can is nearly impossible.  Hence one should hesitate before opening a CanOfWorms.  Opening a CanOfWorms means that you might not be able to make the resulting unpleasantness go away.

''We use PandorasBox for that version of events. Either way, it's not good.''

The CanOfWorms is the same thing, just not as bad - it's impossible to close PandorasBox, but cleaning up after opening a CanOfWorms is simply unpleasant.

''Can - open.  Worms - '''everywhere!'''''

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See WhatIsEntropy