You seem to be quite passionate about the ethical or aesthetically pleasing way to implementing following in a web application. Passion is cool, but I'd encourage you to think of what HN would be like if two ways to think about user following routinely resulted in "Please get off the Internet."

I do not necessarily disagree with your normative beliefs here. I'm just saying, as a positive statement of empirical reality, an application which is designed to work like the one you have described will perform worse than one which works like the emerging standard of autoinvites. Measurably worse. It's kind of like Girl Wearing A Headset photos: without saying they're either pleasing or tacky, one can make the observation that they've been tested to death hundreds of times and they generally increase conversion rates.

This kind of "positive statement of empirical reality" tends to (1) be true, and (2) make the world a worse place as everyone acts accordingly, until (3) it stops being true and (4) everything goes horribly wrong.

Banking, circa 2007: As a positive statement of empirical reality, selling unrealistic mortgages to unsuitable customers and then packaging up the default risk into CDSes and selling them on will perform better than lending responsibly. Banking, circa 2008: Oops.

Any pyramid scheme, in its earliest stages: As a positive statement of empirical reality, signing up will perform better than ignoring it. The same pyramid scheme, after a couple of iterations have saturated the market of available fools: Oops.

The Dutch tulip market in 1735: As a positive statement of empirical reality, selling everything you've got to buy tulips as the market climbs inexorably higher will perform better than holding on to old-fashioned goods like gold and houses and food. The Dutch tulip market in 1740: Oops.

The personal computer market, circa 2000: As a positive statement of empirical reality, what people want to buy is the cheapest possible computers (or, for a lucrative subset of the market, the cheapest possible computers with impressive-looking specs) running Microsoft Windows. Selling cheap generic boxes will perform better than trying to make something of really high quality, and anything other than Windows is a loser's game. The personal computer market, in 2011: Apple is bigger than Microsoft, many makers of generic beige boxes are frantically trying to get out of the business, and it's a serious question whether "personal computers" in general will get their market almost completely eaten by tablets (meaning, for the present, mostly iPads) and smartphones.

Spamming users' social networks is like selling crappy mortgages, tulips, or mediocre cookie-cutter computers. It may, for the time being, be an easier way to make money than the obvious alternatives, but every time someone does it the world becomes a slightly worse place, and sooner or later it's likely that people will notice and stop playing along.

Of course you're welcome to point out the "positive statement of empirical reality" that spamming works. You're probably right. And you're under no obligation to acknowledge the ethical issues that those of us with tenderer consciences may have. But when someone responds to that with "please get off the internet", I think they've got a point, just as they would have if you'd suggested that startups should lie to their customers, or sell addictive drugs to children, or dump poisonous byproducts into the local water supply, in order to increase their profits. It might "perform better". It might happen not to be illegal. But that still doesn't mean that a reasonable person should be recommending it.