What are the biggest risks of automated trading?

Ranked by realized damage to retail accounts: (1) Oversizing — a fine strategy at 100% of a too-large allocation; position sizing failures dwarf signal failures. (2) Overfitting — deploying a backtest mirage that degrades immediately live. (3) Execution bugs and edge cases — the fat-fingered limit, the order loop, the strategy that didn't handle a halted ticker; platform-level guardrails (price bands, notional caps, kill switches) exist for exactly this class. (4) Regime change — a strategy meeting a market it never saw in testing. (5) Set-and-forget rot — automation running unwatched for months past the point its assumptions died. Note what's absent: 'the bot steals my money' — with scoped, non-withdrawal broker permissions, that risk is structural, not behavioral.