True, Cryo, there are many crimes that are truly 'victimless'. However, these laws are mostly ones that people are not sent to jail for breaking. Charges for 'Victimless' crimes are added to the package of charges to help force a plea agreement, add mitigating circumstances to increase the allowed jail time in sentencing guidelines, or just because they are easier to prove than the 'real' reason the person was arrested.
For a good example, according to the Uniform Code of Military Justice (UCMJ, or the 'law book' that governs all military members), it is a court-martialable offense for an officer to commit adultery. While I personally think adultery can wreak havoc in a home (i.e., it isn't really 'victimless'), most folks would consider adultery between consenting adults to be in the category of a 'victimless crime'. Last time I checked, about 20 or so officers were prosecuted under this statute per year. However, in each case, the charge was not as a stand-alone offense, but usually coupled with charges of rape or sexual assault (charges usually harder to prove beyond reasonable doubt, with only the physical evidence and the vicitm's testimony that the action was not consentual).