I don't know why so many answers are "no". I bought the speakers that this question is attached to, and I am listening to them right now. 2 of them, tethered together. So the answer is YES you can connect them together for more sound.
It just so happens that I have two of these and a Y-jack for headphones, so I tried it. The requirement would be that you have a splitter (Y-jack) plus two USB ports available for two speakers. It did work, and of course was louder than just the one, but wasn't true stereo. I previously had a Y-jack that split stereo to mono, but I'm not sure where it is. If I find it I'll post the results here. Bottom line is you can't daisy-chain these, but with a splitter or even mixer (why?) you can make it work.