A big point as mention by others is which status you are in when you book a ticket. Those that are in Plat. status cant compare with us with bare minimum miles in our accounts.
I recently tried to book a RT to Florida and it was a real hassle only to be rejected at the end for the dates I wanted during peak season. On the otherhand, my friend who wanted to travel with me was in a higher status (since he works for a company letting him use company CC to accumulate alot of miles for himself), he also apply for RT on the same dates and flights and was accepted right away.
Conclusion:for people who have very little miles, it is almost impossible to book any flights to peak destinations at peak times