Well, here comes Slader.com to the rescue. The site has compiled step-by-step answers to the problems in some of the most popular high school textbooks, according to All Things D.

But most interesting to Paywall Times readers will be their subscription model, which can be as low as $1 a month and has members (a mix of students and parents) spend “point” to see full solutions. Users pay for a block of points, subscribe for daily points, or buy “gold” that can be transferred to other members. The rationale for this is that their customers are both parents with credit cards, but also students themselves, who sometimes use pre-paid debit cards, sometimes transfer points to friends, or even use PayPal, according to All Things D.

I spent some time perusing their site, and the subscription models (especially the $1/month promise) seem a bit obtuse and hidden. Furthermore, the whole model seems like it may be a retention nightmare. But then again, playing into a gaming aspect of collecting points instead of focusing on a traditional subscription angle may be the best way to retain high school students. It’s going to be interesting to see what happens and how they scale their services.

Sounds bad, right — more evidence that adding a paywall is a site killer? Except that one metric, whether it’s unique visits, pageviews, or video views, doesn’t tell the whole story.

In fact, Hulu’s revenues were up 90% in Q1 2011, according to a blog post by CEO Jason Kilar. Adding another revenue stream in the form of online subscriptions must have contributed to that growth.

And the site’s paywall hasn’t killed advertising revenues, either: Hulu was the top site on the Net for video ads viewed in March, also according to ComScore.

Obviously, I’m not privy to Hulu’s detailed financials so I don’t know the exact impact their subscription model is having on revenues, or whether the model will succeed in the long run. But I do know that it’s easy to latch onto one metric – like pageviews or site visits – and make broad conclusions about a site’s health or the viability of paywalls in general.

In reality, though, sites with a hybrid subscription/advertising model are always balancing the two revenue streams, and declines in one metric may be offset by improvements in others. You can’t get a complete picture just by looking at a single number.

The email read in part, “Your site is a f*** farce filled with useless information that you throw in with the blatent intent to get users to click on a Google adsense link. Do you think we are idiots? I am sure there plenty out there, but don’t expect me to help you get paid for nothing!”

Thing is, although the web is almost overwhelmingly littered with AdSense spam sites, MyFederalRetirement.com’s content is not spammy. Not by a long shot.

Scott himself comes from a premium content background. In fact, we worked together at B2B premium content companies in the 1990s, publishing subscription newsletters that sold for hundreds and sometimes thousands of dollars per year. So, he knows what truly worthwhile editorial is.

Unlike the majority of crap AdSense sites that exist on new visitors who quickly leave never to return – MyFederalRetirement has such high quality content that tens of thousands of Federal employees and retirees have joined its email list, which has less than a .001% unsub rate, and they return to the site again and again and again. Scott’s editorial team work hard, continually publishing new, expert articles to help their readers. It’s pretty good quality without the premium price-tag.

So why is Scott getting hate mail?

To me, this is a clear sign of an Internet user backlash against the nearly unavoidable TONS of dreadful AdSense-supported content out there. People are sick to death of it.

It’s gotten to the point that when I visit a new site, if I see an AdSense ad block, my immediate gut-reaction is “Oh no, this is probably crap.” It’s nearly the same emotion as when I open an email and discover it’s spam. Nearly any chance of impressing me with the value of your content just went out the window. In fact, having an AdSense ad block is almost like having a big giant “CRAP” stamp on your page.

Chances are for most new visitors, the AdSense block brand is way more famous than your own logo, so it gives more of a brand impression than anything else on the page. You can’t mitigate the branding problem by minimizing the ad block’s visibility. You won’t survive that way. AdSense publishers need to put ad blocks in multiple, prominent places on each page in order to generate income. Top, bottom, side, search box….

Due to its quality and loyal readership, MyFederalRetirement.com is doing fairly well financially. But, the time is coming when Scott may have to reconsider that site’s business model. He’s already begun testing paid content through some of his company’s other ventures. He’ll be ready when the time comes to make the jump.

Google’s made a lot of noise about eliminating AdSense spam sites from their network since the day it started. But, I haven’t seen much progress. Yeah it’s a tough job. In the end, though, there’s too much money on the table for them. Google is in the business of selling online ad clicks. That’s it. They’re not in the business of defending content’s virtue.

That’s the publishers’ job. Don’t wait for Google to “fix” things. If they do someday, fine, we can all go dancing in the streets. Until then, protect yourself. Start testing other business models, because I think AdSense ad blocks may soon be hurting your brand more than they’re sustaining it.

The only other online revenue source that scored even higher, was blog sponsorships, with 56% of magazine execs saying these had profit margins of more than 30%.  Think I’ll call up my friend Henry Copeland at BlogAds, a great network that sells ads across loads of third party blogs,  and see if he wants to get a beer to celebrate!

The sponsorship includes a 14-day free trial of the game online.  This is a classic type of subscription site sponsorship that  I first saw on The Economist’s site several years back.  Then, Oracle was the sponsor. So, it’s an idea transferable across various niches too.