I think the thing with shop advertising is that :
1) It's V Cheap
2) If you get just one job a month from it, it pays for itself.
I put an card in a shop years ago in an area I had no customers in whatsoever.
Got a call and did the house...then did the friends...then her friends...4 years on i do most of the houses not just in her road but surrounding roads as well...just from one 60p a week card!