Will people judge me negatively for skipping department seminars? I'm a graduate student in the Earth Sciences.  The breadth of my departments runs the gamut from geobiology to geophysics and everything in between.  As a result, a large number of the department seminars that get hosted are on topics that I have little or no background in and do not relate to my research field in any way.

The expectation seems to be that everyone should go to these type of events to stay abreast of major events and gain some breadth of knowledge, but whenever I go to one that is far outside my sphere of knowledge I end up resenting the wasted time.  To me, it seems like a huge waste to sit through a 60 minute talk on something I don't have the background knowledge necessary to understand in even a rudimentary way.  Sometimes this is the fault of the presenter for not preparing a talk for a broad enough audience, but with biology talks I know that the fault is my own.  Don't ask me the difference between a protein and an amino acid; I have no idea!

So lately I've felt a strong temptation to blow off some of these events reasoning that it would be vastly better to get in another experiment that day than go sit through a lecture I'm not equipped to understand.  But I'm worried that other people will think I'm being a slacker as a result.

Do you look down on colleagues who sometimes skip out on talks far outside their expertise?

And, Is skipping an event like this better or worse than showing up but discreetly reclaiming time during bad talks by studying on a smartphone?  Obviously, whipping out a laptop during a lecture would be very rude, but flipping through flashcards on my ipod while sitting in the back of the hall would be a low-key way to reclaim some of that time during talks when I have no idea what they are talking about.
I would say that you should always go to seminar, unless you have some very compelling reason not to go (you are away, you are working on an experiment, you are trying to finish writing your thesis, etc.). 

There are four reasons:


Scientific courtesy. To travel somewhere and give a talk to the 10 people who show up (5 of whom you already knew) is really irritating. 
Good or bad -- you learn something about presentation. Even if you say "wow, I should never do that in a talk" your hour has been well spent.
You get perspective. You never know when something that someone says will make you see your own work in a different context. 
The speaker may someday be interviewing you for a job. It's better to be able to say "I heard your seminar" than "Oh, sorry, I missed your seminar when you visited."