Shh! Quiet in the library
The man printed on the cardboard is Mr. Hjerppe, the director of Undergraduate Library in the University of Helsinki. I guess the small "switch your phone to silent mode" signs weren't very effective.
The mobile phone etiquette in Finland is nonextinct. Finns can answer their mobile phones in fine dining restaurant without excusing themselves from the table first or supposedly silent libraries. Mobile network coverage is more or less ubiquitous and nearly everybody have a cell phone.
If finns want to use their phone silently, they'll most likely send a SMS. Phone billing in Finland also works so that using SMS is cheaper than calling - which might be one factor explaining as to why younger people like to type rather than speak their messages.