A small software house LimitNone has filed a complaint in an Illinois circuit court alleging that Google at first began promoting the smaller firm's tool for migrating Microsoft Outlook customers to Gmail, then copied the idea and went into competition with it.

The lawsuit was brought by the commercial litigation firm of Kelley Drye & Warren LLP–by the same team who previously faced off with Google in a trademark case involving the Silicon Valley company's highly successful online advertising system.

Last December, the firm of less than five employees learned from Google that it planned to enter the market for LimitNone's migration product itself because the business opportunity promised to be huge, according to court papers.

Lead plaintiff's attorney David Rammelt said in a phone interview that LimitNone had been told by Google that 50 million subscribers was "just too big to come from someone else" and that a simple calculation of the lost revenue for LimitNone "very quickly gets you up to about $950 million.