Related Clues:

• They're seen on passing buses
• Personals
• Spam, most often
• Paid pitches
• Banners on buses
• Spots on a screen?
• They play during many a bathroom break
• Paid space
• DVRs get rid of them
• TV break fillers
• TiVo users may skip them
• Modern-day pop-ups
• Zapper's targets
• Magazine revenue sources
• Paper back items?