"Yahoo is harmed by Facebook's use of Yahoo's patented technologies in a way that cannot be compensated for by payment of royalty alone," Yahoo's lawyers wrote. "Facebook's use of Yahoo's patented technologies has increased Facebook's revenue and market share because it does not have to recover the cost or time involved in the development of the technology."

While the suit may look like a change in strategy for Yahoo, that's likely not the case, Sterling said.

"The tendency is to see this as a sign of resignation by Yahoo, that they can no longer compete and they're going to get money now through patent litigation because they can't generate revenue through advertising," he said.

However, he thinks Yahoo is just taking an opportunity presented by Facebook's public offering to secure a potential cash infusion.

Yahoo did not reply to a request for additional comment on its lawsuit.