I have a friend who does this and he moves from country to country. He is just a true nomad, he has spent time in around 20 different countries this year alone (all EU and eastern Europe this time).
Unfortunately the hostels he stays in dont have decent internet and its expensive to roam using his phone.
And, as he works for a uk company the hour or two time difference means he is at work when the cafe's are open. Did nobody think of that???
He does ask if he can sit for a couple of hours for work and forward pays for a couple of cups of coffee and a sandwich, so far all of the places he has been in have said yes and he always tips well.
The problem is where someone sits for three of four hours with one cup of coffee. But the owners could stop this easily by not having the for the wifi plastered freely around the place.
Only give the if you spend oh lets say €10 or make it clear that you dont approve of people hogging the seats... Its not rocket science is it???