No, you need to fill the form. I tryed to do the same yesterday but I received reply that for 2011 no referral bonus is available.
This is the email I received from the Diamond desk:

Thank you for your message to Hilton Reservations and Customer Care. It is my pleasure to assist you today regarding your request.
We are terribly sorry for the inconvenience this has caused. Unfortunately, we are unable to activate a referral account at this time, as the HHonors Member Get A Member promotion ended on December 31, 2010.
Mr. WilliamXXXXX will need to activate an account by himself and should a new promotion be offered for 2011 within 30 days from the date of activation, we will be happy to update each account with the referral information. However, at this time, we are unable to do so.
We appreciate this opportunity to assist you and thank you for your continued loyalty! If you have any further questions or concerns, please let us know.


This is strange because on the website the referral info are updated for 2011.
Here are the T&C (bold mine):
TERMS AND CONDITIONS:
Offer is for named recipient only and is not transferable. Offer valid between now and December 31, 2011. Qualifying new enrollments and stays at participating hotels within the Hilton Worldwide portfolio must be made prior to December 31, 2011. Only those eligible stays that take place after enrollment in Hilton HHonors will qualify for HHonors Bonus Point earnings. Offer cannot be combined with other select offers. Bonus Points do not count toward VIP tier qualification. New HHonors members who enroll via the Member Get Member program cannot merge their accounts with any other HHonors accounts. By communicating this offer to potential HHonors members, the referring HHonors member agrees to provide his/her name and/or HHonors account number to potential enrollees. Due to privacy law, Hilton HHonors cannot share any new member’s stay activities with the referring member. Due to our privacy policy, we can not inform you if your friend is already a member of Hilton HHonors; if you submit their name, they will simply not receive this email invitation. Each HHonors member can refer up to 10 new HHonors members and earn a maximum of 25,000 HHonors Bonus Points from now to December 31, 2011. He/she will earn 1,000 HHonors Bonus Points every time his/her eligible referrals join and complete a stay at participating hotels within the Hilton Worldwide portfolio. Each new HHonors member will earn a maximum of 1,000 HHonors Bonus Points after his/her second completed stay by December 31, 2011. Hilton HHonors Worldwide, LLC. may disqualify any person for any HHonors Bonus Points based upon fraud, dishonesty and violation of the Member Get Member Terms & Conditions or the HHonors Terms & Conditions. Hilton HHonors Worldwide, LLC. reserves the right to replace, withdraw or limit HHonors Bonus Points or free night certificates in the Member Get Member Promotion at its discretion and without prior notice. All decisions regarding the interpretation of rules, eligibility, etc. for the Member Get Member Promotion lie solely with Hilton HHonors Worldwide, LLC., whose decisions are final. Hilton HHonors® membership, earning of Points & Miles® and redemption of points are subject to HHonors Terms and Conditions.