It is rare to notice an offensive word being displayed on number plates by any road going car. The simple reason for this is the authorities who sell the combinations for custom number plates tend to pick out what they may see as offensive to be used on road going vehicles. These combinations are then permanently removed from sale.
On previous occasions it has been noticed that often authorities who sell the right to combinations sometimes miss out a few potentially offensive combinations which be sold onto someone and eventually end up on a car. On these circumstances the authorities, such as the DVLA for UK registered cars, often inform the number plate owners to remove their custom plates in order to be refunded for the money they initially paid. These kind of circumstances can occur when authorities like the DVLA realise the combination being displayed is potentially causing offence to other road users.
Recently in the UK, an individual who purchased the registration 'BO11 LUX' was ordered by the DVLA to remove it from his car as it was causing offence. The combination was purchased from the official site and the owner stated that it created plenty of laughing faces when it was noticed. The owner of the number plate bought it for his new Range Rover he was due to purchase in March 2011. The idea was to assign the plate 2011 number plate to his new 2011 registered vehicle, however, a month later the combination was requested to be removed.
There are tighter measures now on clamping down on drivers that use combinations that cause offence. DVLA have made it clear that motorists should not use combinations that refer to drugs, alcohol or profanity, some slip under the net, but watch out for personalised number plates you go for, if it is deemed as offensive or blacklisted, DVLA can easily remove them.