During my 4 years in Canada I went to the US around 20 times. I came back same day on all my trips, only once I stayed for 2 days there. I had I think 2 stamps or 1. CIC had no problem with this at all.
Keep in mind I live on a border city so the CIC officer told me she goes to the US all the time too.
Keep in mind I live on a border city so the CIC officer told me she goes to the US all the time too.