It depends - the closer you are to the city center and I think that this applies to almost every city, the more stickers dominate. At other places outside the city center 'classic' graffiti becomes more important - depending on the neighbourhood.Have you noticed an increasing use of already printed stickers instead of either painting or using a stencil?
The fist time I have seen it as well, but on the other hand, having seen 4ever quite often, the idea is ot that far off..."5ever" is rather witty. first time I've seen that!
That's simple: There are places where graffiti is allowed, these are the legal places. Illegal refers to the rest.