Granted, this is from the Daily Mail, which tends to the alarmist and anecdotal, so take it with a grain of salt:
Toddlers these days are barely out of nappies before they are playing with touch-screen toys and fiddling with iPads.
And now, it seems, they are paying the price – because when they arrive at nursery they are apparently struggling to pick up basic fine-motor skills such as holding pencils, pens and crayons....
[L]iteracy expert Sue Palmer said: "I think what children really need up to the age of seven is real life in real space and real time, which means three-dimensional experiences.
"We already have problems with children not being able to hold a pen or pencil. But we are giving our kids instant gratification all the time with ICT and it makes it harder for them to persevere with something that takes a while to learn. There is a real fear that too much engagement with this quick-fix technology is making it more difficult for some children to learn how to read and write."
There's no citation for the claim that using tablets erodes fine motor skills among young children, so file this somewhere between "anonymous experts claim" and "a guy in a bar knew someone whose cousin had seen it happen."