Recently, I saw a gentleman who did not disclose any dates on his resume. It turns out that he had a medical condition that prevented him from working for several years. He did not want this lapse in employment to hinder any job opportunities.
Any recruiter reviewing his resume would surely question the lack of employment dates, and perhaps disregard him as a possible candidate. My advice to him: put the dates back on the resume and explain the lapse in employment within the body of your cover letter.