It's not the bribery but the reciprocity and equality. When does it create an obligation? Another example is bringing food or drink. Generally when we bring

It's not the bribery but the reciprocity and equality. When does it create an obligation? Another example is bringing food or drink. Generally when we bring comestibles to share, no one expects to have to reciprocate, because we're all sharing. But if you offer the host a gift, it creates entanglements. Generally I try to shift the frame to the shared activity - eating, brainstorming, gaming, etc. so people feel that if they are participating, they are contributing. For dinners out, I don't think rich people should presume they have the right to pay before anyone gets a chance to contribute. It takes away the agency of others.