"Right circumstances" includes support for your cause and rapport with your audience, such that most of them don't feel manipulated. The one time I saw that method used, the speaker already had the audience in the palm of his hand, such that they felt they'd already gotten their money's worth just from having listened to him. The stand-up/opt-out trick was just to push an already-high expected conversion rate higher.

(An example of how good a rapport he had: early in the presentation, he asked that people please promise to not even attempt to give him any money that day... and several people laughed and shouted "No!")

Of course, I suppose if you're that good, the trick is moot. On the other hand, the public approach your synagogue used is equally manipulative... it just builds the conformity pressure more slowly, instead of all at once.