Ask any founder about their very first users. They’ll more than likely gush over how grateful, excited, blessed, and even suprised they are that some group of strangers chose to spend time using the thing they built.

That adoration is often mutual. Early adopters feel a special connection to a service they joined, taking pride in “discovering” something special before it hits the mainstream. It’s even stronger in network-focused services, where a community forms among those initial, core users.

But you know that thing annoying music snobs do with bands, where, the minute an artist breaks through to the mainstream, suddenly they’re sellouts?

Well, it happens in consumer Internet too. The problem is that bands, once they’re mainstream, don’t need the hipsters anymore. Startups, on the other hand, still need their core users. In fact, the way a startup navigates the tricky transition from a niche service beloved by a small but rabid fan base to a widely adopted, mainstream product can make or break it.

I’ve noticed a handful of examples of this phenomenon in recent weeks. The first was at SXSW. It seemed a very hip thing to talk about the good old days of the conference, before it got so noisy and crowded and overrun with marketers. Some people I talked to seemed bitter that the 20,000-person conference was no longer an intimate gathering of the tech world’s brightest minds. The theme was “big is bad.”  (As a first-time attendee, I wanted to ask, “Then why are you here and not home, complaining on Twitter?”)

Then, while there, I ran into some disgruntled people who’d arrived on a StartupBus. They were upset that StartupBus, now in its third year, had grown into something much bigger and, in the process, lost everything renegade and exclusive and cool that they had loved about it. Badge-less riders weren’t allowed into the finals event. The organizers cared too much about press. The unique culture so beloved by the original “bus-preneurs” was gone. They told me they were going to start their own version of the StartupBus to take it back to its roots.

Then, just after Instagram announced it would finally launch on Android, I had a conversation with an avid Instagram user that left me speechless. He, and others within the Instagram community, were upset that the service was launching on Android. It would double the amount of users, he said, and add more bad, low quality users to the network.

Plenty of similar murmurs echoed around the Twittersphere yesterday as one million Android users downloaded Instagram. The guy I spoke to and other prominent “power-Instagrammers” have been considering taking their “business” to EyeEm, another photo sharing app with, presumably, far fewer users than Instagram. (Ironically, EyeEm is already available on Android.) As an Android user, I’m a little insulted, and secondly, COME ON!

Each of these instances made me want to roll my eyes and tell these people to get over it. Change happens. As someone who isn’t among that core group of users, this kind of thing comes off as absolutely, 100% ridiculous. What right do they have to complain about the growth of a free service they happen to be way too attached to?

But the goal of a startup is to get people to care about and love their product. These people do; it’s hard for a founder to tell just them to STFU. I can imagine it’d be pretty easy to fall victim to pleasing the users — the people who for some insane reason care so much about something you built that any change to it breaks their hearts.

Those broken-hearted fans can just as easily turn into bullies. Digg might be the most extreme example of catering to core users. The company surrendered to the community’s rallying cries. Whether you attribute Digg’s fall from Web 2.0 darling status to that or to other factors, the service has basically been supplanted by sites like Facebook and Twitter. It has lost its chance at mainstream adoption. Meanwhile, both Facebook and Twitter are examples of services that managed to survive the expansion from niche to everywhere. Facebook did it mostly by ignoring the angry cry of the mob.

It’s tough to keep slogging away on a product that doesn’t have at least a few hardcore users that love it. And without them, it’s even harder to get a company off the ground. But ultimately, the only way to you build a big business is with a big user base — purists be damned.

[Illustration by the awesome Dana Zemack, whose blog is here]