Unable to takeover Groupon after the latter rejected its $6 billion offer, Google has opted to start from scratch with its own daily deals-giving service. Google Offers is initially rolling out in Portland, New York, and San Francisco, where it will provide discounts of 50% off or more at various retailers, presumably using the same time-limited group buying formula as other deal sites where the discount is only activated once enough people buy into the offer.

Only sign-ups are open right now, but offers should come soon. Like Groupon, Google will be distributing their offers via regular emails, which will "let you in on amazing offers in your area." As you'd expect, Google is not auto-subscribing their users to this program, they are asking users to sign-up for Google Offers via the Google Offers landing page.

It's unclear if Google will be integrating this service with other of its web products like Places and the 'formerly known as Hotpot' recommendation engine, which could boost the effectiveness of Google Offers.

There are still some doubts on whether online services like Groupon are at all sustainable. "You get what you pay for," they say, and unfortunately that's been the case for me the couple of times I've used these sites to score a discount. Businesses sign up for Groupon on the premise that the deals lure new customers who will then come back willing to pay full price. But often they can't handle the overwhelming flood of coupon holders, who end up getting second-class citizen treatment. So businesses actually spend money in customer acquisition but don't see them coming back.

That may be a generalized view and one could argue that you should only buy into offers for places you know and like. After all, it is rumored that Groupon is getting ready to go public at an estimated value of $25 billion, so they must be doing something right. What about you, have you had any experience with these deal of the day sites?