More to the point, like many bloggers I use tips from e-mailers all the time -- so often that I've come to rely on them. The vast majority of these tips are simply links to other published sources, not original bits of inside info.
Yes, and I suspect that many of the e-mailers are in fact bloggers of some sort themselves. I think this is the main way you rise through the blogging ecosystem. You find something interesting, you blog it yourself, perhaps with a little comment, and then you e-mail the link and comment to the highest profile blogger you can think of who you think might find it interesting, in the hope that they will give you a link. This is why a blogger etiquette system in which it is considered good manners to link both to the source itself and to the person from who you got the information, whether this is from another blog or through e-mail, has arisen.