"AFAIK Google adsense for search comes with its own everything (searchbox + searchresults + ads) and there is no API to simply fetch ads on the query terms."
This is where you are wrong. Google does give out XML ad feeds.
Are you kidding me?
Keep writing naked puts and then compound it by assessing your risk based on historical data.
This is a surefire way of loosing your shirt when the next Lehman level event comes around.
The risk in your strategy is that the stock market has very fat tails and unlikely events happen with more regularity than they should -- and the math that you're using to assess your risk discounts all these events by terming them unlikely.
I made my first site bulder product in 1999, went up against the biggies of the day in massive corporations (Vignette was a favourite one to beat) and won most pitches. Only we called it a 'Content Management System'
The first dot-com crash wiped out the product/company.
The big difference I see now vs then is that then you were selling site builders, now you have to sell complete marketing solutions. A product that makes a good site is not enough, you need to deliver the entire value chain. Right from SEO/SEM to the being the primary directory of the industry to having custom sites for each merchant better be available thru your platform.
This is what etsy and opentable do, this is what you have to do.
And doing this across industries is HARD. Though many of the components in the industry vertical products may be common, there are enough unique business processes in each vertical that doing a category leading job in multiple verticals is just not possible.
If you want to build a real-estate site builder, you need to compete with realtor.com, for restaurants with opentable, i'm sure there is (or will be) an equivalent for lawyers. Competing with one of these behemoths is challenge enough, now imagine fighting against all simultaneously.