I have seen alot of diversity regarding the etiquette of who pays if a group of people go out to a restaurant to celebrate someone's birthday. It looks like people expect one of three things:
- the birthday boy/gal is considered to be the host and pays for everyone
- it is considered to be a gift to the birthday boy/gal so everyone pays for their own plus covers the meal of the guest of honor
- everyone just goes dutch, including the guest of honor
I typically follow the last option and expect everyone to go dutch unless the dinner invite is phrased as an invitation to a party (then I expect the party host to pay) or the friends all decide ahead of time the dinner will be a gift to the birthday boy girl (then we chip in for their diner too).
I know this has been debated alot, particularly in the context of the bill being split unfairly (which always happens) but I wanted to get the concensus of what everyone expects when invited to these dinners.