Get great coupons and early notice delivered to your e-mail
Safeway's "Just 4 U" program is probably the best example of the benefits of giving your e-mail address to a grocery store. But I have found that just about every chain has something to offer in exchange for your e-mail.
There is the issue of spam, of course. Every large corporation swears that it won't sell your e-mail address, and they may or may not be truthful about that. The larger issue tends to be light-fingered employees. In my experience, a lot of security leaks happen because some low-level button-pusher gets bribed into handing over a copy of the company's database of customer e-mail addresses. A list like that, of verified good addresses, can be worth a lot of money on the open market.
But assuming that you have a reasonable spam filter, frankly I think the risk is worth it. (Your mileage, as they say, may vary.)
At the very least, most chains will e-mail you when their new ad circular is published. This can save you a trip to the mailbox, as well as sometimes give you a free preview of what's coming up so that you can plan ahead. If you like to shop in the next area over to get other deals, you can plug in that area's zip code instead of your own, and have the deals e-mailed right to you.
Many chains offer special e-mail-only coupons, if not all the time. I find that small stores are more likely to do this, as a way to entice people to come in, and as a reward for signing up for their e-mail list. There are a few local yarn stores which offer e-mail-only coupons, and as a knitter, I am glad to be on their lists.
Others simply make it more convenient for you. This morning I got an e-mail from Fred Meyer with two coupons, one of which was for 10 percent off all household furnishings and furniture. I'm in the market for a desk, and while these coupons would be available at the physical store if I went there, I would not have realized they were available if I hadn't gotten the e-mail. That's a pretty good extra value!
The only down side to e-mail coupons is that you have to print them out yourself. And I don't know if you have noticed, but printer ink is one of the most expensive commodities on the planet. (Psst, print them out at work, if you have access to a printer there!)