I've been to St Petersburg six or seven times in the last 15 years, but the crime problem has really gotten a bit worse lately. And I would not have been aware of how to protect myself, or even what to look for if I'd only relied on the local St Pete press or local tourist mags or brochures.
Thankfully, as I flew into Moscow earlier in the month, the (English language) Moscow Times had an article on the increasing number of (foreign) tourist crime victims and how they were being victimized--in St Petersburg!
This may also go on in other European subways, but I'd never seen it in Russia until this year. The article described how tourists would get surrounded by a group of four to eight thugs and how they'd go through his/her pockets/bags very quickly, then scatter off the train, before the doors closed and even before the person realized they'd been robbed.
Being a Russian speaker of Russian parentage and walking with local Russian friends, I thought I might blend into the crowd. Not likely, as apparently even the way we foreigners walk/carry ourselves (and our shoes) are giveaways that show we're not local and likely have a foreign passport or camera or cash or something else they might want. As we walked underground between Metro stations, they spotted me as an "easy mark" and prepared to strike.
As my friend, his wife, and I waited for the train, there were only three other people waiting with us. BUT as the train pulled in, the doors opened, and the disembarking folks started out, we were surrounded by a "rush-hour type" crowd. Also, one of the bad guys had run into the subway car through another door and started pushing behind the folks getting off. Meanwhile, the ones behind us were pushing us INTO the train.
My friend was in front, and his wife was behind me. We had not planned specifically for this, but it's probably what saved me.
Also, anytime I get into a crowd-type situation, I reconfigure most of my stuff.
I had reslung my daypack/rucksack onto one shoulder, in front, carrying it like a rugby ball. My jacket was tied by the sleeves, around my waist, blocking access to any pants pockets.
This all happens very quickly as they try to do the deed and get back on the platform before the doors close. Normally (and this is rare, I've been told), if a passenger is accosted on the train, there's a call button in (each?) car to notify the driver to lock the doors and not open them until the police open them at the next station. True or not, the thugs want your stuff and to get back to the relative safety of the unprotected platform. Now, there is a police presence as you enter a Metro station at the turnstiles, but that's it. It's VERY RARE to see them elsewhere, so the thugs are pretty free to rob and run on the platforms.
Back to my story: as were being pushed into the car, my friend in front felt someone trying to grab his fanny-pack, which he'd turned around to the front, and my friend's wife started getting yelled at by the leader(?) of the thugs, as if she was blocking him getting onto the train (but in reality, she was blocking ME from THEM). All the other passengers were distracted by this screaming fellow, and we still didn't realize that we'd been accosted or attempted-mugged or whatever you want to call it.
When the guy (30ish years old and the dead eyes of a former "guest" of the State) didn't get onto the train and and two other guys got off (who had just gotten on with us), we realized what had just happened--that they'd tried to rip me off. We were extemely lucky, as I'm sure their success rate is pretty high.
Long story short: Don't assume you're safe in a crowd, don't drop your guard ANYWHERE, and be prepared for someone grabbing your stuff, be they gypsy kids or teenagers or older guys wearing black leather jackets. We did see the same guys the next day, in the same station (Gostiny Dvor), and while they saw and recognized us, they didn't try it again, so maybe that's the best way to deter those kind of guys: make eye contact and let them know you see them.
I don't mean to scare anyone off of visiting this beautiful and really amazing city, that's not the point. While it may be inconvenient for you, keep your valuables in hard-to-get-to places. Also, be aware of your surroundings and of those around you, and while many Russians are quite hospitable and friendly, don't assume they're all that way!
I've also heard the cops in Russia are REALLY ineffectual after the fact, so it's REALLY unlikely that if you get robbed, you'll see your stuff again, so just DON'T get robbed is the best advice!
I've since heard of these kinds of attacks happening in Madrid and Italy and other spots in Europe, so I know they're not exclusive to Russia or St Pete, but it was still kind of sad.