There have been a few such reports circulating around the Tweet sphere which starts to make it seem like a real problem.
Streetsblog have done a good job on some arguments against it - one 'survey' was done that used spurious data.
A governor in New Jersey is calling for texting while crossing the road to be made illegal
Distractions are important if you are in control of a vehicle. That is when harm can be caused.
If you are distracted using your legs you are more likely to walk into a lamppost.