Hi,
If you meant selecting/adding multiple contacts in a form using the InfoPath (2007) built-in Contact Selector control, I believe this has been one of its limitations - yes. You would need to add code in your form to achieve this.
Have you considered Qdabra's Contact Selector template part which allows selecting multiple contacts? You won't need to write the code yourself because it's using qRules. I suggest watching this video for more information, see if it meets your needs.
Let us know if you need any help and we'd be more than happy to assist.
Best Regards,