Along with the wider bars the trend is toward shorter stems. A wide bar effectively slows steering and increases reach, and a short stem counteracts this. Many people find the handling characteristics desirable with the wide/short combo. On the other hand, it can bias your weight rearward on climbs or simply be too wide in very tight forested trails.

Myself, I am comfortable for now somewhere in the middle, with 26.5" bars and an 80 to 90mm stem for cross country and endurance riding and racing. But I like to play around, so maybe I will go wider next season, especially if I am riding more singlespeed than geared (the extra leverage helps). But while the extra leverage is nice when standing, a very short stem can cause some wheel lift on steep climbs. Just riding around, I can deal with this, but in the second half of a long race I don't like to feel like my bike is working against me on the climbs. So intended use matters a lot.

Like other people have said there is no right or wrong answer.