switching/prediction makes up a ton of competitive battling. WHen you switch with spikes on, you get hurt, therefore, you have to either stay in, and let the opponent bring in a counter, or get hurt every time you switch. So, really, if you have three layers of spikes down, then the opponent has a huge disadvantage.
Good Spikers:
Forretress: The spikespinner. Can lay down spikes, as well as rapid spin spikes away. Good defenses to back it up. Use with suicune to kill.
Skarmory: The phazespiker. The most used spiker, for it's good defense, plus it's ability to learn whirlwind/roar so it can keep on roaring to get hurt by spikes. Plus, with it's typing, basically no physical hit can hurt it without a boost, as it cannot get hit by earthqake. Plus, the only reason people use Magneton.
Cloyster: Another spikespinner. Similar to foretress, but more weaknesses.
Deoxys-LG: Spikes in the uber metagame are killer. Hardly any teams carry a spinner. Use with WW lugia to kill. However, lots of ubers have levitate, which tones this incredible pokemon down
