If you ask someone if something can or can’t be considered ‘mainstream’, the usual response involves numbers. User numbers, audience numbers, profits. Stuff like that.
The thing is that the idea that large audiences = mainstream is essentially fallacious. You tend to get much larger audiences for mainstream things, but not always. Something that is mainstream can have very small numbers indeed. Then we say it has ‘niche appeal’. Quite a lot of things we think of as mainstream fall into that category.
Our normal reaction is to think that something that has appeal to the majority of society (more than 50%) is ‘mainstream’. Untrue. Barbie, for example, appeals primarily to teenage girls in the age 6-12 range. That’s definitely niche appeal, but we accept that Barbie is mainstream.
The Olympics? The Beijing Olympics was the first to top a 51% of television watchers. It’s struggled over the years to get a larger number of people to tune in even once during the event, but again, we consider it mainstream.
Football? Estimates vary, but it seems to be about 30%. Again, mainstream.
So, to be mainstream doesn’t mean that you have appeal to a majority. Most mainstream things do not.
Gaming is clearly not yet mainstream, even though its audience is over 50%. So, absolute numbers and percentages don’t tell you anything about how mainstream something is.
Instead, some consider “mainstreamness” to be the quality of appealing to a broad range of demographic segments; Genders, ages, and educations.
If so, then Second Life hit the mainstream good and hard a while back. But we know that it is still not mainstream.
The answer is simpler.
If a lot of people think it is weird or peculiar, then it isn’t mainstream even if it has majority appeal.
Barbie only has a niche appeal, but the majority do not think of it as odd. Therefore, it has become mainstream.
The Internet and the Web still are riding the borderline, slowly moving towards the mainstream, but not firmly a part of it yet.
You want to be mainstream? Stop being weird, ease off the use of any unusual terminology or domain-specific language or … just wait until your weirdness is the norm.