Contact bounce on a switch feeding a lamp is usually harmless, but it can cause trouble for a counter circuit. Why?

1. 1The lamp draws more current than the counter, so the bounce is hidden by the load
2. 2The lamp warms up slowly, but a fast circuit sees each bounce as a separate operation
3. 3The counter circuit has no ground connection, so it ignores slow signals and misses the bounce
4. 4The bounce drops the supply voltage below the counter's limit for a few cycles