Is there a particular niche / segment where email marketing wouldn't be successful?!?

Anti-Spam filters?

Personally I hate email from insurance companies promoting their products. I dont know if Im alone.

Adam, you might have to expand your definition of email marketing a bit if you want to tackle a niche like electronics. Yes, someone who buys an LCD TV may be interested in a laptop, but that's throwing mud at the wall to see what sticks.

Try to think more laterally. Someone who just invested in a fancy TV might be interested in a home theater rig. Or content to play on that TV. Or additional TVs for other rooms in the house. Or...?

You may also have to face the idea that some people, having satisfied the urge of the moment, will simply lose interest in what you offer. Meaning you may have to look at 'restocking the list shelves' more often than someone catering to, say, a dedicated golfer or cat lady.

Email marketing for service businesses can work extremely well. You offer the information as you said above, but do not hide the fact that you offer such services. Don't wait until you've delivered a certain amount of content before making an offer. Add a soft offer (like a PS) to every message. Then, after a few of those, you can hit them with a special offer. To use your example,

"Okay, now you know what superior web design can do for your results, and you know how to find a designer who can deliver a superior design. You know it might take time to find such a designer in a crowded field.

What if you could shortcut the whole process?

You can. Hire me.

Here's a special deal I only offer to folks on my list, and it's only good for ten days or until x number of people snap it up..."

If you have good testimonials, you could include a few, and/or link to a page with more.

In your next emails, you go back to delivering information, and for ten days worth, your PS reminds them of the time left in your special intro offer. Don't worry about 'ruining the relationhip', as you are not looking for a prom date. Both of you know that you are in business, and a fair offer is expected and welcomed (if you set the proper expectations going into the process).

I can't think of any niche/topic/area where email marketing wouldn't be successful as long as it is done right. Email marketing is not only sending promotional emails that contain affiliate links. Consider email marketing as a means of communication, building relations, educating and helping others, sharing valuable information, etc. it is not only about selling.

you want to join that niche ?

Well yeah in a nutshell email marketing will always work. Even in the niches you described. You're talking about how to monetize that list down the road. You could set up many ways to connect with them and send promos, but you need to establish what they want first. Why are you collecting their email in the first place? What do they get out of it?

There are ZERO niches that I can think of where email marketing would not make you money.

Some niches might not be as profitable but every niche can make you money.

It is not a lie that "The Money Is In The List"