Jefferies analyst John Colantuoni expresses concern about eBay's advertising growth slowing down significantly in 2024, dropping from 23% in Q4 2023 to just 4% in Q2 2024. This decline poses risks for both gross merchandise value and EBITDA, as slowing growth will limit margin and reinvestment capabilities. Colantuoni emphasizes, 'We expect slowing advertising growth to eliminate a key source of margin and reinvestment capabilities, resulting in downside to both gross merchandise value and EBITDA.'