At times, I may be speaking to someone and think it would be a good idea for them to contact someone else:
"Oh! You should really speak to [insert name here], let me find [his/her] contact details for you..."
Other times, the person I am speaking to may ask me to provide a list of contacts:
"Could you send me a list of people you think could help with [this project]?"
Is it acceptable in either or both cases to share someone else's contact details with a third party?
If someone's details were to be shared, is it essential to then contact that person and let them know (even if there's no guarantee the third party will get in touch)?
If I wish to share someone's details, is it best to ask them first and, if it's not possible to do this, is it best not to share that person's details?
(An example of when it might not be possible is in the case of situation 1 above, where it would be weird to say:
"Excuse me, I'll just call [insert name here] and ask them if they mind me sharing their details with you..."
Another example might be when the third party has time restrictions, or the person you wish to share the details of is not available.)