This depends on the industry you are in, and the kind of people you are leading. Many industries are low-margin and have constant cash flow issues.

Telling your employees achieves nothing, in that case - their next job won't be less precarious, they just lose a little bit of piece of mind. You make the active choice that some (who want to see you as a crook anyways, see other replies) think slightly worse of you, while the vast majority can go home and sleep in relative peace.

It's a very different situation if cash flow crunch is completely unexpected, or highly likely to be fatal, with stable businesses around.

As I said above, the situation is always more complex. You make decisions accordingly :)