A mortgage interest rate below 2.48 per cent, determined by the number of "likes" the promotion gets on Facebook, is the latest bank bid to generate customers.
The ASB Like Loan, which will land one buyer with a low fixed-interest rate on a home loan for one year, ran for one day on Facebook yesterday. Last night, the Like Loan was set at 2.4732 per cent.
The winner will be notified at 3pm today in the first of a series of four similar social media promotions by the bank, which attracts 70,000 followers on Facebook.
It's the latest in a string of attractive prizes including flat-screen TVs and iPads offered by banks to sweeten home loan deals or entice new customers.
The promotion is being hailed a success by ASB, with more than 800 Facebook users sharing the app with their friends by yesterday afternoon.
ASB brand experience and digital channels general manager Anna Curzon said feedback had been overwhelmingly positive to the promotion which was developed with Saatchi & Saatchi to tie in with the bank's other online campaigns.
"Like Loan will allow us to use our strong Facebook following as advocates for ASB as they 'like' the loan to lower the rate and will give four people the opportunity to win a great value fixed home-loan rate."
Social media commentator David Slack called the promotion a "bargain" for ASB.
"That's easy for them because only one person gets it, everybody's talked about it, and it's only one year's interest forgone," Mr Slack said.
"I think they're getting themselves a bargain and they know it. From the point of view of the one lucky person it's a nice saving but it means that everybody else is roped into it to do the marketing for ASB for nothing by sharing the buzz around."
Mr Slack said so much of modern marketing took advantage of people's labour for free.
"Even if it is just as trivial as clicking a like button. We're too stupid to realise that we're doing their work for free for them."
He called it a clever campaign.
"They're genuinely innovating here and I'll give them credit for that, but they won't give us credit for anything."
Massey University senior lecturer in banking Dr Claire Matthews called the promotion a gimmick to gain attention.
"One lucky borrower is going to get a really good interest rate for one year but the reality is for everyone else they're stuck with whatever ASB is offering.
"It's just another way of getting their name out there and generating some interest."
She said the idea was working it had generated a lot of interest in one day.
"I think it's a way of getting people involved and participating. It's quite a novel idea."
ASB Like Loan
• The chance for four Facebook users to win a low-interest home loan rate.
• Rate is lowered with each "like" the app receives.
• Fixed for one year on up to $500,000.
• Open to existing and new customers.
• Promotion runs every Wednesday for four weeks.