I have used offline methods such as flyers to promote online products for several years now. I've never done much analysis of where my clicks and sales were coming from, but it always seemed to me that the offline clicks were better quality. The reason I came to that conclusion was that I'd usually get more sales in the weeks and months after doing some concerted offline promotion.
I'm pretty sure that assessment was correct because I've just been promoting an affiliate program using both methods. The network has really comprehensive stats and they reveal a pronounced difference between the results generated by each of them.
I have one banner on a web page that I've been promoting solely offline, and over the last month that ad has received 58 impressions and 8 clicks. I have another banner for the same program that is on one of my blogs. Granted, it's an eclectic blog, not specifically related to the affiliate product on offer. But it's had 988 impressions over the last month with only 4 clicks.
As yet, I haven't had any sales of that product. Still, there's a pretty noticeable difference there. And I think this is mainly due to the fact that if someone goes to a website as a result of seeing an offline ad you can be sure they're reasonably interested in what it offers. They'll also type it in, meaning they'll give it their full attention for a short while at least.
The same cannot be said of various forms of online promotion. Sure, search engines are very targeted. But even then people are often whizzing through them quickly, flitting from query to query. And blog and site hopping is not so targeted, and often happens when the searcher is a bit bored. It's more a kind of grazing behaviour than anything focused.
That's why I think offline promotion of sites is worth doing. It's pricier, slower and more laborious. But it can still be profitable.