Airplane Seat Reclining Etiquette

If you google "Airplane Etiquette", numerous articles pop up.  All of these articles talk about how rude it is to recline your seat all the way back during flight.  What do you think about this?  Is reclining your seat ok?  Does it matter on the plane size? 

I say this because I am a horrible flyer.  I get motion sick each and every time I fly.  Yesterday, in route from Detroit to Minneapolis, the guy in front of me reclined his seat ALL the way back - just as I thought I was going to throw up (Yes, I did think about puking near his head).  I was thankful it happened to me and not my boyfriend Ross, had it been him it literally would have crushed his knees.  It got me thinking, where are we on this reclining thing?  They estimate that if someone reclines all the way back, it takes away about 20% of the little room you do have. Do you think it's rude, or was I just not feeling well.  Thoughts??