Opera's infrastructure might be overwhelmed by Facebook's traffic, but the company has been beefing up its servers, according to its most recent financial statements. In the first quarter, Opera spent $2 million on infrastructure, a 66% increase over the same quarter the year before.

Other parts of Opera would also be attractive to a buyer like Facebook, including Opera's three mobile ad networks -- -- the company's new payment processing technology, dubbed "Opera Payment Exchange;" and its existing relationships with scores of carriers and handset makers.

And Opera's revenues are on an upswing.

First quarter revenue was $47 million, up 28% from the same period in 2011, with the biggest share -- nearly $17 million, or 36% of the total -- coming from the search deals Opera has with Google, Yandex in Russia, and Baidu in China for its desktop browser. Like rival Mozilla's Firefox, Opera generates most of its search income from Google.

Search deals for Opera Mini -- again, Google and Yandex -- brought in another $3 million, while the company's ad networks contributed nearly $7 million, a 303% increase.