For your future reference, I have an email address and answer at least half of all questions asked to it. (100% for elementary school teachers.)

1) Providing value in a scalable fashion in SEO is hard, because Google has an incentive to make it hard. If SEO were only as hard as AdWords, Google would lose billions of dollars. Google considers virtually any repeatable process that improves rankings to be black hat. I don't enjoy having to joust with a giant team of PhDs who have infinite budget.

2) The SEO tools space is hard. Small-scale website owners are often very skeptical that there is positive ROI in SEO. (There is positive ROI in SEO. Crikey, if you learn one thing from me this year, learn that.) You have to do huge amounts of teaching to raise people to the point where they can begin to benefit from it. That starts, literally, at "What is a search engine?", because most website owners do not know, especially in small business.

For marginally savvier website owners, like the average HNer, you can skip some of the teaching and proceed directly to "I don't want to pay you money for this." You've been on the same HN I have for the last year, right? We talk a good game about raising $50,000 each of a dozen angels and valuations in the tens of millions and whatnot, but what happens every single time someone suggests raising prices past, oh, $20 a month?

http://news.ycombinator.com/item?id=1510986
http://news.ycombinator.com/item?id=1780348
http://news.ycombinator.com/item?id=1357592

SEO makes me thousands a month. I'm not interested in selling it for less than many hundreds a month, at the low end.

3) Enterprise sales is not my idea of fun. Selling SEO to people who really would seriously benefit from it -- companies which do a lot of transactions online -- requires a high touch sales process. I'm not incapable of that -- I do it for consulting -- but it isn't my passion in life, and it wouldn't scale easily without me building a sales force. That requires a whole lot of skills (hiring, managing salesmen, showing up promptly at nine to an office somewhere, etc) that I don't have experience with, natural aptitude for, or any reason to suspect that I'd be really good at.

4) What would it do, really? (Your "real" question.)

Broadly speaking,

+ SEO analytics: Hard to demonstrate value. Most obvious feature sets are well represented by free competitors. Significant competition from SEO training providers who like to throw in a bag of tools subscriptions to make the $N00 a month fee look cheaper.

+ Tools which purport to "do" SEO for you: if it works Google will call it black hat, if it doesn't work it is snake oil. I have seen an awful lot of snake oil.

+ Demand Media In A Box: Probably the best SEO tool I can think of writing -- automate topic selection and direct outsourced production of content for it. Let's hypothetically pretend that I both was capable of and wanted to write this: what is my incentive to selling it to people who pay little money and need lots of handholding when instead I could point it at any problem domain I wanted and make a million dollars each time?

5) What is the opportunity cost?

I'm pretty good at what I do: I make and sell software, and I do occasional consulting for other people who mostly make and sell software. Consulting is fantastically lucrative, and would (and has) helped me get together enough money to launch any software/service I care to.

I picked out one I thought was a good bet, and am busy implementing it. Ask me next December, but I am cautiously optimistic, in a way I have never been optimistic about SEO tools.

THAT SAID:

There may be a profitable, addressable market for SEO tools. There certainly is for SEO-related training/services -- SEOBook and SEOMoz are both doing quite well. YC has funded at least one SEO-related company.

I wouldn't touch it with a ten-foot pole, though.