We do our own ads with digital projectors and a computor program. By doing ads in house you can be much more reasonable in your ad rates and make more profit. In house control allows you to place the content that you want.
For instance we stress discount Mondays, real butter, digital sound and the availabilty of gift certificates. We also do public service ads free for local non-profits such as the animal shelter, rape crisis etc. And of course we have 8-10 ads running at any given time.
We used to use a large company for slide advertising but are much happier controling the content and pricing ourselves.
In general my philosophy the last couple of years is to eliminate all middle men so as to be a leaner more efficient business, thus in house advertising was a must.