For example… When my laptop is running at 2.2GHz (just web browsing or playing some flash games), it's decently quiet but I can still hear the fan, and the air coming out is only moderately hot; when it goes up to 2.4GHz or 2.5GHz, (when playing Minecraft it usually does this) the fan kicks up in to semi-rocket 747 mode and all of a sudden hell is blowing out of the vents. Do frequency increases really make that big of a difference? The CPU itself goes all the way up 2.8GHz (it's an AMD A8-4500M APU) but given how hot it already gets I think the CPU would melt at 2.8.
Btw, these frequency readings are taken from the Windows Task Manager, if that makes a difference.