If you look at the Careers page for Paris you'll notice that a lot of the places listed aren't cool places to work, they are service companies re-selling developers to other companies. And the same is true for the job listing search.
They are called IT Staffing firms and really aren't great places to work. Sometimes they provide jobs for customers that are great to work for but that isn't what is listed on their Stack Overflow Careers page, and they nearly never provide this information in Job offers.
Careers should provide a way to filter them and remove them from the view.
And I also think that this filter should be ON by default at least for the cities pages (like Paris). In the current state Careers can't easily be used to distinguish great places to work for.
Some staffing firms can display impressive Joel test results, a beautiful location and great facilities. But if you choose to work for them they will send you out to a client with no good practice, not facilities for employees, etc.