Hm, I'm going to go against the consensus here.
There are different types of machine and hand finished hems. For machined, the two most common I've seen are the napkin type, which unbelragazzo above has mentioned, and then there's a sort that Gerald covered here
. It's this picture:
All of my Drake's and Rubinacci squares are finished in this way.
Hand finished hems aren't as easily categorizable. I would only differ them in terms of quality. I have some that have been very nicely done, and some that look like they were made blindly. The worst handrolled hem I've seen was on a cream silk Brioni pocket square. The best was on Vanda (assuming you like neatness and tight rolls. You can prefer something else of course, no reason that you can't). Here's Vanda:
As you can see, handrolled hems have nothing to do with swelled edges, "imperfections," or many of the other things people have stated above. I see no imperfections in Vanda's hem, and both techniques here have rolled edges. I don't know if handrolled is an indication of quality either. There have been members here who have made their own pocket squares by handrolling mediocre fabrics they source from a local store. I wouldn't say those are better than Rubinacci's silks.
Napkin type hems are indeed terrible looking, but I would actually prefer a machined rolled hem over a poorly handmade one. It has a nice braiding effect when done on silk (not apparent in Gerald's photo), whereas a poorly made handrolled hem just looks uneven, loose, and sloppy.
If I have time, I'll try to take photos of some of my pocket squares tomorrow to illustrate, but in general, I wouldn't say there's anything wrong with a machined hem. I love my Drake's and Rubinaccis. If done well, a handrolled hem is only "better" in that it adds some kind of artisanal value. It just means someone put the time into finishing the edge. That doesn't necessarily make it perform better or even look better, it's just a labor intensive thing you appreciate or you don't.Edited by dieworkwear - 10/3/12 at 10:32pm