The standards for articles on bloggers and singers have to be high, because there's a huge number of bloggers and singers out there trying to promote themselves by writing on wikipedia about how awesome they are. Since nobody has the time or the inclination to police the article on Joe Blogg's Blog when it claims that "this is the awesomest blog on Earth", wikipedia tries to limit the number of articles on subjects where the article's editors are likely to have a strongly vested interest in the subject of the article.
Another reason: every obscure animal and flower species on Earth has been around for millions of years, and most of them will (I hope) be around in another million years. Towns usually have lives measured in centuries. The average blog will be forgotten (even by its author) in a few years.
If they're not high quality, said famous people are likely to sue or otherwise cause hassle for Wikipedia. That's something a rare flower is not likely to do.
The closest it's ever come was this incident:
http://en.wikipedia.org/wiki/Wikipedia_biography_controversy
where some guy's article stated for years that he was a suspect in the Kennedy assassination. He never tried to sue wikipedia, though he did complain a lot.
Incidentally, though, this shows another reason why wikipedia articles on borderline-notable people are bad: the fewer people look at an article the more likely it is that crazy non-facts will persist in the article.
[1] http://arstechnica.com/tech-policy/news/2008/05/dumb-idea-su...
[2] http://www.citmedialaw.org/threats/american-academy-anti-agi...
While I don't agree with some of the policies on the English Wikipedia, you also have to consider that having articles about anything incurs a long-term maintenance cost on the project. This especially true when the articles are about living persons or controversial subjects.
People are always complaining about Wikipedia because some obscure subject they personally care about didn't make the cut. Meanwhile there are literally millions of very useful encyclopedia articles on topics that unquestionably belong in an encyclopedia.
It's that sort of content that Wikipedia mainly caters to.
This is the problem. Wikipedia takes its lead from encyclopedias, but it's not an encyclopedia, because it's fundamentally different. It doesn't have the same space constraints, it isn't written in the same way, it isn't referenced in the same way, etc.
"Does this article feel like it belongs in an 18th century concept of an encyclopedia" kind of test for inclusion or deletion in Wikipedia just seems wrong-headed to me.
I've never understood why those who do want wikipedia to be wiki-random-non-notable-factia don't just start wiki-random-non-notable-factia. I predict it will be fairly unmaintainable, but I'm totally keen to be proven wrong.
I suggest that you start an "expanded Wikipedia" project with more inclusionist criteria. I'll be happy to contribute, although I'm pretty happy with the English Wikipedia's notability policy. I'm sure thousands of other people will be too, especially if the result is any good.
Jimmy Wales already did something like this, by the way.
Articles about random Internet personalities or some garage band are thus inherently not in the scope of the project, until they become more notable.
If you write articles purely in certain controversial areas, like recent internet memes, I can see running into a lot of problems. But the vast majority of areas don't really have any rampant deletion. I've written articles on mathematical formulas, on prominent computer scientists, on important physics books, on 18th-century politicians, on famous paintings, on well-known children's toys, and on varieties of cheese, among other things, and never gotten any problems with any of them.
Wikipedia will happily include every obscure city, animal and flower species on Earth (see http://en.wikipedia.org/wiki/Schizothorax_yunnanensis_yunnan...), but will try to delete articles on bloggers and singers that are very well known within their niche.
I don't get it. Adding additional pages to Wikipedia does very little to reduce its value and plenty to increase its value (always coming up first in Google to give a basic overview). No one is going to read or print the whole thing anyway. Whether it's 3.3 million or 13.3 million articles doesn't seem to make a difference.