Do fellow airline passengers refuse to respect your personal space? Then Create A Space of your own. Got a seat mate who hogs all the space on the armrest? Create A Space for your elbow, and yours alone.
Some will probably balk at the pettiness and curmudgeonry of bringing a partition onboard a flight to delineate your side and "their" side, but I say let's step back from arguing with each other about items like the Create A Space and Knee Defender for a moment and think about who this animosity should really be aimed towards: the airlines. If they gave us enough room, and gave one foot (literally! That's likely all it would take!) about our comfort to begin with, there would be no need for these guerrilla measures.
As it stands, the guerrilla Create A Space says it will help reduce the stress of flying--both dealing with elbow and hip checks from the person next to you, and trying clamor to your seat first to claim the arm rest--with a rigid, fold-up flap that hooks over the arm rest and drapes down the gap in between it and your seat. Create A Space both divides arm rests down the center, and extends upward a few inches to make a ledged wall for additional support.
Collapsed, the Create A Space is about the size of a book, and weighs 10 ounces.