Overclocking processors generally voids the warranty and in general overclocking isn't something that appears in marketing materials for most or all processors.
Actually the box of my AMD FX-8320 reads:
* Unlocked out of the box
* Achieve ultimate power with up to 5.0Ghz and 8 cores
* Overclock your system for supercharged performance
The joke is when you read the included papers inside of the box:
Use only the heatsink/fan provided. Use of any other heatsink/fan will void warranty