The recruiting company is in the business of placing qualified people in paying positions. Following up is absolutely part of the process as the recruiter generally will only make money if one of their candidates is hired into the position. They may have one or several candidates in line for the position and they usually solicit feedback from varying levels of formality with the company. Usually a recruiter new to a given company will spend more time solidifying the contact with the company staff to make sure that they are meeting the company's needs.
Ideally, the recruiter is looking to both improve his own communication with the company as well as making better selections in the type of candidates the company recieves. In a perfect world, the company won't blame the screw up of the recruiter upon the interviewee - for example, when an Interviewee doesn't get the info that the recruiter should have passed along - but it's not a 100% perfect system.
How the recruiter takes the feedback is another story. Ideally, a recruiter will realize that if the communication got confused, they had a part to play - but each person and company is different.
How long and how diligently a recruiter tracks and maintains this info is another story - one that is very much dependant on each recruiter. Long ago, I worked with recruiters who assimilated a very accurate profile of me as a candidate, and did an excellent job at recognizing my strengths and weaknesses - it was very personal and I had a 1 on 1 contact. Lately, I've had cases were recruiters don't seem to talk to each other or keep a shared data store of any type - because a "do not call" request to one recruiter does not stop the onslaught of spam-like emails from his collegues... so mileage here is highly variable.