Since AC/DC is also a commonly used term to refer bisexuality, its use on a porn site would seem to be a legitimate (at least as legitimate as a porn site can be) use of the domain, and would not indicate registration in bad faith. I can easily see an electrical contractor or supplier to also have a legitimate claim to the domain. WIPO is full cybersquatting complaints, it is also full of actions where someone wants a domain that they feel that only they should have and they are slapped down.
Registering domains with the sole intention of selling them to someone else who has a claim on the domain when there is no direct legitimate claim of their own to the domain is cybersquatting, and is illegal in most parts of the globe. Using it for another purpose, such as registering a common term (and AC/DC is a common term in the the electrical engineering field) and directing it to a search engine (or even a porn site) is not cybersquatting. If the term is trademarked, however, it MAY be trademark infringement, but generally only if the site it advertises or sells goods or services that compete with the trademark holder.
If I registered theregister.biz and pointed it to a web site that sold point of sale equipment (cash registers), it would be a legitimate use of the domain. If I pointed it to a news site it would be trademark infringement. If I did it to sell it to the folks that run this site it would be cybersquatting. If I had it pointed to the point of sale equipment and theregister.co.uk asked to buy it from me, it would be a legitimate business transaction. If I had it pointed to the point of sale site and then tried to sell it to the folks here it would be a "gray area" in the law.
Anyway, cybersquatting isn't really a major problem and hasn't been for quite awhile. The real problem that I see these days is "domain tasting" -- upwards of two thirds of all .com domains registered are actually "tasters", not squatters, and they don't stick around long enough for you to file a complaint against them.