wrote a post about how Mac users with iLife are legally entitled to use any music or loops contained within without limitation. However I had comments that people have had a problem with using them that I have also encountered myself. The problem is that when uploading to YouTube, videos using iLife music sometimes fall foul of YouTube's automated Content ID system.
YouTube is a hotbed of copyright infringement, and attempts to solve this are understandable. The Content ID system works by companies, on behalf of copyright holders, uploading a digital file of their work. YouTube scans uploads for registered works and (depending on the copyright-holder's preferences of individual works) either blocks the offending video outright, or slaps banner ads on the video that generate income for the copyright holder - a kind of compromise between the content creators infringing copyright and copyright holders.
So far so good, but it's evident that this is open to big problems and abuse. I encountered this myself when uploading a "how to" video I'd made, which contained the iLife track 'Jaracanda'. Soon after uploading I got an email saying I'd breached copyright, and found my video hampered with annoying banner ads. I put in a dispute about this, and the notice was soon removed, but it's an annoying process to go through when you're using music legally. It's worth noting the copyright claim wasn't from Apple Inc, but some from some obscure agency with almost certainly no rights over iLife music.
There are two possible issues at play here. Firstly is the ease of the Content ID system to be fooled. This example shows a situation where the uploader has legally used an iLife track only to find YouTube claiming the copyright belongs to a rapper who had (presumably also legally) used the same loop as a backing track. Sometimes the track is misidentified completely. A weirder example is this story, where a video had a notice slapped on it for copyright infringement on the soundtrack - despite it containing no music whatsoever, just a guy foraging for salad in a field (what makes it even more amazing is that the copyright claimant upheld the claim on dispute, although in this case it was almost certainly administrative error rather than any fraudulence).
More disturbing is those that claim illegitimate copyright on royalty-free work, meaning that they are hijacking the work of others and getting money for nothing. This webpage, by Patrick McKay, lists some examples of companies that have been accused of this, and criticises YouTube for not requiring any proof whatsoever from copyright claimants of their legitimacy. It means companies can reap ad revenue from royalty-free, public domain and Creative Commons works they had no hand in creating.
It seems making a dispute on incorrect copyright claims will (usually) result in the copyright claimant removing their notice, and this should always be done (if it's iLife music, quoting Apple's terms and conditions never hurts). When a dispute is wrongly contested it gets harder, as YouTube's policy is that disputes can only be made once - if the "copyright holder" upholds it, that's supposedly the end of it.
Whether through malice, genuine human error or software issues, users shouldn't be slapped with legal notices when they're doing nothing wrong, and companies certainly shouldn't be profiting from ad revenue on material they did not create.