Apart from the fact that then, you're not visiting them all on a single trip, so by the time you get to the 5th or so, you can't remember the 1st any more (If you don't pay projects attention, they die).
A while back I know the owner of this site did a few hundreds $ per month. It was really an eye-opener to me :)
Of course this requires SEO skills to earn more than a few bucks, that need to be learn on the way.
I started a couple of sites like this one, and although I earned a bit of money, I wanted to try sites that are really useful to myself, which I'm focusing on now.
I think it's always good to remind myself that between what would look a half-spammy site to a regular programmer, and the typical too complex projects regular programmers would start, there's a sweet spot in the middle.
Is there a generic webapp (something like OSCommerce) that can automatically create an affiliate store like the one you linked when supplied with a list of item names or URLs?
iPhone apps. 2 of 3 of them use the standard free+ads, paid+features model. The other, my most successful, is strictly paid at $1.99.
They were a lot of work up front and some have required minimal maintenance- but supporting them hasn't even taken up even 2% of my coding time in the past year.
Maintaining 400 projects is impractical, but it is possible to create 400 micro-businesses that don't need to be taken care of.
For example, you can create a website, write 10 high-value blog articles and make a landing page for a product you want to sell that is related to the articles. (This costs <$10) You have to put in the initial hours to tweak the content, maximize conversions and get good SEO, but after a certain point you can just let go.
Of course, you will get nowhere near the revenue you can get if you put in the hours to actually build the business. But if the purpose of the site is to maintain a certain level of income (like a lifestyle business) and grow no more, then this is definitely feasible.
Jeremy Schoemaker (online marketer) uses exactly this approach. 1) Find a niche, 2) create a product to help people in that niche, 3) create a system that will stay intact even if you don't touch it for a year.