UPDATE According to a Google spokesperson, Google Trends was not hacked. The spokesperson gave the following statement to the Huffington Post concerning the irregularity on Google Trends:
The Hot Trends list is automatically generated by machines and algorithms that detect hot or breaking queries. On June 17th, a questionable term appeared on the list for a few hours following a surge of search activity for the query. To be clear, this was not a hack of Google's systems. While we have filtering mechanisms in place to help prevent objectionable and automated queries from appearing on Google Trends, no filter is 100% accurate. We're continually updating and improving our filters in order to provide the best user experience possible.
Google Trends, a tool that tracks the most popular search queries, seems to have gone awry.
Earlier this morning, the top spot on Google Trends was occupied by an offensive phrase ("lol" followed by the N-word). Other trends have included generic terms such as "pet shops," "gift shops," and "dentists." (see screenshot below)
It's not clear what's causing the problems appearing this morning, although Google Trends has been hacked in the past. In 2008, the top term on Google Trends was replaced by a swastika, then later, the phrase "ǝlƃooƃ noʎ ʞɔnɟ."
At the time, Google told TechCrunch that the problem had been caused by a "link on a a popular Internet bulletin board:"
The Hot Trends list is automatically generated by machines and algorithms that detect hot or breaking queries. In this case, it appears that the html code for this query was posted on a popular internet bulletin board, which led to quite a few people searching to find out more about this symbol. The Hot Trends list reflected that surge due to people searching with this query.