Hi Toqual
In your hypothetical it is not clear exactly what kind of personal information (eg, street address, email address, phone number, other) your friend is disclosing and to whom (eg, a third party business, individual, other). However, in general a person's express consent should be obtained by a third party seeking their personal details
If your friend provides your personal details (eg, email address, phone number) to a third party business which uses that information to send you unsolicited commercial messages (eg, ads in emails, texts), the business may well be in breach of consent requirements under applicable legislation. The Australian Communications and Media Authority oversees anti spam legislation and the Do Not Call Register. You could consider contacting their department which best fits your query:
http://goo.gl/Rvx7HD
And of course you can let your friend know that you would prefer if they first ask for your permission in the future before handing out your details!
Hugh