Despite my earlier jokey posts, there is a serious side to all this.
Speed is sometimes fun, but can always be dangerous. On your own in a car on deserted motorway or somewhere i would say is ok for pushing it a bit, as you only have yourself to blame or injure if it all goes wrong, which it can (richard hammond??) plus you are not putting any other innocent road users at risk.
Silly speeds and rural roads is a very bad thing, as is acting like a race car driver on the roads if you have passengers, i can literally lose count of mutual friends, plus three very good mates that i have lost due to excess speed on unsuitable roads and road conditions, and every one of them was either a passenger, or an innocent party involved in a collision with a rally wannabe or a drink driver.