Common pitfalls

Most failed gamification is built on a bad assumption: that adding rewards to a task automatically makes people want to do it. The traps below show up again and again.

The points, badges, and leaderboards (PBL) trap. Putting a scoreboard on an unengaging task rarely fixes it. If the underlying activity has no meaning or feedback, the scoreboard just measures how little people care.
Crowding out intrinsic motivation. Rewarding something people already enjoy can make them enjoy it less once the reward appears. This is the over-justification effect, well documented in Self-Determination Theory (SDT) research. Be careful adding extrinsic rewards to intrinsically motivated behavior.
Over-relying on pressure mechanics. Urgency, scarcity, loss aversion, and fear produce fast action. Under The Octalysis Framework those are Black Hat drives, especially Core Drive 8 (CD8): Loss & Avoidance and Core Drive 6 (CD6): Scarcity & Impatience. They can also burn people out or breed resentment: short-term metrics up, long-term trust down.
Designing for the designer, not the user. People are motivated differently (see Hexad and Bartle). A leaderboard motivates competitors and demoralizes everyone else.
No clear objective. Gamification bolted on without a defined target behavior produces vanity metrics.
Manipulation and dark patterns. Mechanics that exploit compulsion (especially around kids, finance, or gambling-adjacent products) carry regulatory and reputational risk. The field increasingly treats ethics as a core competency.
Set-and-forget. Novelty fades. Systems that never evolve lose their pull. Onboarding, mid-game, and endgame all need design.

A rule of thumb this community tends to agree on: if you stripped the points and nobody would still want to do the activity, fix the core experience first.

This page is part of the r/gamification community wiki.