Seems to be another online currency - this one tied to the price of gold.
You get up to 0.25 grams of virtual gold on signup - which is about $12 AUD currently.
This might be a good way to get some exposure to gold.
While the deal is still on (and the link still works). They are now playing silly buggers with the amount you get and reclaiming inactive balances (where there has been no deposit). I'm going to mark as expired therefore.
Edit: Some updates
There have been some recent changes to the referral program - the amount received is now linked to the "Golden Heart level" score of the referrer and does not seem to depend on country anymore.
The exact details of these changes are outlined here.
Part 11 of the Bitgold Terms of Service deals with promotional balances, and may be worth a read also.
Things to note:
Everyone to date seems to have got their bonus regardless of making a deposit.
OzBargain user lolmao successfully withdrew 3g (~$125) to an Australian bank account.
If you have not made a deposit and then don't log in in any 60 day period, they will reclaim the bonus. Consider depositing $0.03 USD of bitcoin to get around this.
Other offers:
Free Birthday gold. This offer is for a free 0.0XXg gold where XX is your age. You get this automatically on your birthday. This promotion is still running as of Jan 3, 2016.
5% first deposit bonus up to $100. I think you get an email with this offer shortly after joining. Mentioned in this tweet.
0.25g of virtual gold (~$12 AUD) for signup via referral link
http://bitgold.com/r/XXOnfK (this is a 5 star "Golden Heart level" link)
I've made a FYI blogger page that contains more general info about Bitgold (interviews, etc).
lol