Well I have had second hand experience with this. When in Paris many years ago on a girls trip to Paris (ah, those day's before marriage and children) and we were aware of pickpocketing on the metro so did think we were being careful. We all had zip handbags and kept our hands over the middle of the zipper part and pulled the bag close into our bodies. My friend (hence the second hand experience) had her hand over the middle of the zipper part but they were still able to unzip the bag to her hand and take her wallet out, WITHOUT HER KNOWING, we were blown away.
Anyway, now older and wiser and travelling with a young family to Paris for the first time since that incident, we are planning for pickpockets as I have no doubt we are going to look like (and sound like) tourists!
We travel all over the world and have never had a problem with pickpockets but as my only other visit to Paris had a pickpocketing incident, we are going to try and be a little prepared.
I have just found these antitheft bags and we have each got one, (including a small one for the kids to carry their own wallets and camera etc) and they are just amazing, they have wire mesh inside the lining to stop bags and straps from being slashed, they have these hooks for antipickpocketing and they say antisnatch too, I was so excited when I came acorss them the other week, thinking, we are getting these for our trip in December. Although I did get them here in Australia, they are not an Aussie product, so do sell them in stores all around the world,
www.pacsafe.com . They are all sizes and shapes and have other travel antitheft accessories including slash proof neck and waist pouches and wallets that clip on.
Anyway, when I saw this thread I thought I'd share my find as I was very excited when I found them (I know, the fact that I get excitement out of finding a travel bag is a little sad, but oh well

).