Here is my 2 cents:
Online marketing can serve as another way to better segment your marketing dollars. So, while you can do “email reminders” to reinforce direct mail drops, you can also allow customers to choose how you communicate with them, giving them more control over how they interact with your company. This will allow you to increase the relevance and the effectiveness of each channel.
Another approach is to use offline marketing to drive customers to an online “funnel” where you can identify the customer and serve-up targeted offers or content. The value of offline is that you can do mass-communication reaching millions, but the weakness is that it’s not interactive–the customer can’t respond to your offer on-the-spot. So, use offline marketing to drive to a micro site where you can provide more depth, as well as breadth, of information–and customer-unique targeted offer.
I’ll ad to my initial answer that another power of using online as a response tool for offline marketing is that by using an “opt-in” mechanism, you can actually measure your promo costs ahead of time and get more “intelligence” out of the whole campaign. At my current employer, we do opt-in promotions tied to a customer’s spending habits, so we are able to track ahead of time what the total max cost of the promo is going to be months ahead of when the rewards are delivered.
A couple other LinkedIn members had some good ideas, including this one from Ms. Jennifer Woodard:
If you have an brick and mortar store, your online marketing can support your offline marketing my including your address to your store and hours on your website. You can offer specials on your website that have to be presented in the store to be taken advantage of. You can offer in your store places to sign up for your company newsletter, refrigerator magnets with your company information and website address, etc.
I think the key here is to let the customer choose his/her preferred “channel” to shop, rather than having pre-conceived notions about what customers want. Otherwise, you won’t see the response rates you are hoping for.