Decay Force #2: Competitors Copy You

The second driver is competitive. If a channel works, it gets crowded. Competitors watch what's working (with ad-intelligence tools, or just their own eyes), copy the tactic, and bid on the same audience.

Crowding hurts twice. In auction-based channels, more bidders directly raise prices, so even a stable clickthrough rate delivers worse economics. And when several companies run near-identical messages against the same users, response rates fall for everyone: the tactic itself gets used up.

This is why case studies are a lagging indicator. By the time a growth tactic has a conference talk and a blog post, the arbitrage it described is mostly gone. First-mover advantage in a channel is real, but it erodes on a timer that starts the moment the tactic visibly works.