What do you ladies think of speedos on guys?

I got the nerve up to be adventurous again, and I wore the speedo that my female friend gave me to the beach. I'm very fit, tall, and not overly hairy or anything like that. As the first time, I was surprised how many women glanced/looked/stared - but still mystified by the giggles/whispering to friends, or laughing. Why do women laugh at speedos? What do you ladies think of them?