This is a great topic!
The gang element was mentioned already, so that's a modern fact we have to cope with. But I have never heard of any particular gang using a rosary for a symbol, so you shouldn't have to worry about getting shot for "stepping on their turf" with the wrong accessories.
The trend comes from the prison ministries, where volunteers would bring rosaries into the prisoners on visiting days. The prisoners would put the rosary on as a necklace, because they were forbidden from having jewelry, and that was all they could wear instead of a chain or whatever.
Prison life is hard in many ways, sometimes it is unbearable, dangerous or even fatal. Any way you look at it, it's not a joke. It's serious business. Whether a particular inmate grew in devotion to Our Lady by wearing her rosary, or not, it has become commonplace for released prisoners to find comfort by continuing to wear their rosary after leaving prison. They have associated it with consolation and a sense of self-worth or self-respect. And it may also carry sentiments of achievement for having survived prison, because many do not survive it.
I absolutely HATE IT[/i][/u] when I see people wearing Rosaries. It drives me crazy and makes me want to chin-check some of these people. The people who I see doing this, however, are the kinds that place no significance on the importance of it.
Unfortunately though, they're the product of their environment and probably don't care about whether or not it offends us as Catholics. To them it's a fashion symbol and there's nothing short of doing something illegal that we can do about it, really.
This is an unfortunate attitude, and I highly recommend that you step back and consider changing your mind. You can do that. Wearing a rosary is not inherently offensive to Catholics.
In fact, St. Louis Marie Grignion de Montfort, the GREAT APOSTLE OF THE ROSARY, was renown for using it to physically draw unbelievers and critics into the Faith. He would put his own rosary over their head and around their neck, and gently pull it toward himself, as he spoke to them, and he was known to claim that never did he do this without positive effect, usually it resulted in the conversion of the person he so drew in. It would seem that he had a kind of charism that Our Lady gave to him, such that her infinite reservoir of graces would open up for St. Louis Marie as he spoke to his subjects. I have never tried this myself, but I told one friend about it and he was quite interested. He said he was going to try it on his daughter! I'll keep you updated with any news!
There has never been any incident of violence, hate or crime in the context of a rosary being worn, as far as I know. Please inform me if I'm wrong.
The new trend of rosaries-as-jewelry has taken a bit of an odd turn, however. There is a website you can go to, ItsHot.com, in the jewelry district of New York, where extremely expensive rosaries are for sale. They generally make all orders up special, since they have such an enormous variety to choose from, but they do have some items in stock. Some of their rosaries cost tens of thousands of dollars, and are made of solid gold, silver, and precious stones including diamonds. Unfortunately, and this is the kicker, it is common for the design to have the beads spaced other than as a rosary, and their excuse is, that the jewelry designer chose the spacing that was "right" for that particular necklace, since it is intended to be used as a necklace, and not for a set of prayer beads.
This trend is now branching out to other manufacturers, so that overstock.com and other online vendors like that have "rosaries" for sale that have such things as 4 decades, 9 beads in each "decade," 3 beads between the cross (not crucifix) and the centerpiece, too much or too little space between beads, and other anomalies. Sometimes there is a clasp in the back, instead of the 5th decade, or else a clasp next to the centerpiece, which would seem to be a distraction for me, but perhaps you'd get used to it.
In the end, there is a difference between what one would have for looks alone or as a practical set of beads to finger while praying. But it is quite possible to have the best of both worlds, to have a rosary that is very nice to use for prayer, and is also very attractive as a necklace. It seems to me that natural stone is a typical match for these two uses. Onyx, jade, pearl, garnet, blue goldstone, amythist and jasper are very attractive, and there are others as well. Hematite is fairly common for very good rosaries, but I'm not that thrilled with it, personally. But I don't know why.