They are a huge problem in the city where I went to University, constantly draining police resources to deal with petty crime. Everyone I've talked to in front of house roles absolutely hated dealing with them as well, if not stealing they always seem to find hair in something and so get a refund or a discount.
Where I grew up they caused huge problems when they moved camping ground, draining council resources and never clearing up after themselves. They left huge piles of litter in the most beautiful countryside spots.
There is an interesting documentary about UK Gypsies called 'Big Fat Gypsy Weddings', it's worth a watch if you're interested in that sort of thing. http://www.channel4.com/programmes/big-fat-gypsy-weddings
Edit: And I don't like the 'well you must be racist if you think this' comments here.