Facebook gets served patent lawsuits all the time, but very rarely by publicly-listed companies (*cough* Yahoo *cough*).

Late last week, however, Canadian communication and collaboration software maker Mitel Networks (Mitel) filed suit against the social networking giant, alleging that Facebook has infringed on two of its patents.

According to the complaint, which is embedded below, the patents-in-suit are:

– U.S. patent number 5940834 – “Automatic web page generator”

– U.S. patent number 7292685 – “Pro-active features for telephony”

Mitel says it has sent letters to Facebook notifying them of the potential patent infringement in July and again in September 2011, but that it never received a response. The software company says it is seeking damages “adequate to compensate for that infringement in an amount that will be ascertained at trial, but in no event less than a reasonable royalty”.

The firm, which was founded back in 1973, offers a wide range of messaging, collaboration, mobility, virtualization, voice and teleconferencing solutions to self-reportedly more than 100,000 customers worldwide. Mitel has partnerships with VMware, Research In Motion, Oracle and (Facebook investor) Microsoft in place.

Mitel is listed on NASDAQ and currently boasts a roughly $182 million market cap.

The company recently released its latest quarterly financial results, reporting $4.4 million in net income on $164.4 million in total revenues.

A Mitel spokesperson sent me the following canned statement:

Mitel has filed a lawsuit against Facebook in the U.S. District Court of Delaware, alleging infringement of two Mitel patents. Mitel actively licenses its patents and protecting our IP is a fundamental part of our business. Available details are contained in the complaint.

As the matter is now before the court, we will not be elaborating further at this point.

We’ve also reached out to Facebook and will update as soon as we get a response.

Mitel vs. Facebook