Agreed. Also once you are in the network of the headhunters you will receive many positions directly (check spam folder too!!!). Some will be unrelated, some may be of real interest.
And yes, keep a track of companies/positions/cities - some may not disclose the client directly unless you work with them, so the same position may be presented by several headhunters.
As a general unspoken rule, they only submit your resume to a company with your approval.