Wikipedia has been a remarkably successful "group knowledge" project. Over 3 million English-language articles have been written by many millions of "editors". Articles can be written and edited by anyone. Wikipedia has no formal review or fact-checking process. It operates under the theory that many eyes will spot and correct errors and abuse.
Wikipedia has become the de facto "go to" site for students, business people, and journalists searching for facts and knowledge about almost any topic. While many academics frown upon it being used as an authority, it does largely provide users with accurate summaries and an appreciation of consensus opinion on controversial topics. Many use it responsibly as a jumping off point for knowledge (visiting its linked external sites), not as an end point for knowledge.
Because Wikipedia has become both the default first stop for casual researchers (and many times their only stop) and a form of gateway into more detailed third party knowledge, many people have tried to "game" Wikipedia for their own ends: public relations, advertising, inserting links to drive traffic, etc.
This is a strategy that largely backfires as almost every article has dozens or hundreds of people who watch it with hawk-like intensity. Such overt attempts rarely last long and frequently end up in an "edit war" that rarely ends favorably for the person trying to use Wikipedia promotionally.
It is, however, not always clear to new users, even those with the most honorable of intentions, about what is allowed into the online encyclopedia. You might spend considerable amount of time entering a write up about your company only to find it gets locked and deleted for not being "notable" enough.
So You Think Your Company should be in Wikipedia?
Golden Rule of Wiki: Never Edit Yourself
It's generally considered in poor taste if you edit an entry you have a vested interest in. For example, editing (or creating) an entry about your own company would be considered a conflict. Ideally, Wikipedia believes if you're important enough to be written up for Wikipedia there should be third party users who are aware of your company and are willing to write you up.
In practice, it doesn't hurt to get the ball rolling yourself. Wikipedia keeps track of the IPs of editors so if you choose to start a "stub" devoted to your company, you should not edit from an IP that's traceable back to your company.
Are You Notable?
Naturally most people think their company is notable. You wouldn't be working for a company you didn't think had something notable to offer. If you own a company, you're unlikely to be devoting your life to an endeavor you don't think is notable. Great frustration can be had on Wikipedia when you try to write up a company or product that seems manifestly notable only to have that entry deleted and locked by upstream editors who disagree and seem intractable in their disagreement.
Wikipedia has several "tests" to determine if a topic is notable enough to be entered. Before you create a topic, you need to ask yourself if the topic fulfills the following "tests":
Significant coverage: Has your company or product been covered in a significant way by TV, newspapers, magazines, etc.?
Coverage Source is Notable and Independent: If the source is, say, a local university newspaper, Wikipedia tends to judge that as a non-notable source. A company newsletter would likewise be non-notable. A notable source would be a daily commercial newspaper, a local TV station, etc.
Awards: Has your company won an important and notable award? What's a notable award? Well, in a somewhat circular way, if the award is in Wikipedia then it's arguably a notable award. Hence, an Emmy award is a notable award. A Lucite trophy given by a local organization of auto dealers is not a notable award in Wikipedia's view.
Get Notable
There is a certain irony that Wikipedia, which is a "dead tree" media killer, waits until dead tree media (newspaper, magazines, books) determine the notability of a topic. There are many emerging trends (and key players) on the Internet that frequently don't get noticed by traditional media. Unfortunately, Wikipedia seems very committed to its current notability guidelines and until such time it loosens them, the ability of small- and medium-sized enterprises getting a neutral, facts-based write up into Wikipedia is slim unless the company has received significant news coverage.
As a first test, you might enter your company name in Google News and discover if your company has received any significant media coverage. If not, and you are determined to get your company into Wikipedia, you should develop a media strategy to get covered by your local daily and local TV station. It's pretty hard to prove coverage on TV as few TV stations keep stories online. However, you can capture your segment and host it on YouTube as proof your company has received significant coverage.