Google (NASDSAQ: GOOG) has recently made a big push into the business software market with its Google Apps service, but has yet to gain any significant market share in small companies.

Google states that it has over 2 million small businesses using their business applications, but the reality is of those, only several hundred thousand of those are using the paid service, and many of those are sole-proprietors and individuals. Microsoft (NASDAQ:MSFT) in contrast, has over 500 million businesses paying for their Office desktop business products.

Google CE,O Eric Schmidt has went on a marketing offensive for its small business applications, which started in the U.S. in August, and is now being expanded to Canada, Britain, France, Singapore, Japan and Australia. The primary marketing strategy is to target traffic hubs where business owners would travel or commute like airports and transit stations. In America the campaign was largely promoted using billboards in several major cities.

Google has been fighting an uphill battle with their online business apps, not only because of their entrenched opponent Microsoft, but also with a few reliability issues with their own infrastructure, such as the recent technical glitches has disrupted service with their Gmail accounts. These outages have generated some concern, warranted or otherwise, about how stable and reliable the Google Web-based software apps, making numerous business owners reluctant to take what they view is a risk.

Google has made some in-roads to the small business software market, but it has a long way to go. Very few businesses have fully adopted Google’s platform for their information services and the company still has a long way to go before toppling other enterprise software companies in the business world.