Well, it was bound to happen. It seems that Apple has grown tired of Mac-clone maker Psystar and finally filed a lawsuit against the Miami-based company, accusing them of violating Apple's licenses and trademarks, as well as copyright infringement.
Psystar claimed in April that it was to offer a $399 Mac clone running at 2.2GHz with integrated GMA 950 graphics. Despite some initial setbacks and concerns about their legitimacy, the company finally began shipping the clones in May. Apple's EULA specifically requires that OS X be installed only on Apple-branded hardware, but of course Psystar maintains that it is doing nothing wrong and that those terms might violate US monopoly laws.
As part of its Mac clone business, Psystar has promised to provide customers with altered versions of Mac OS X system updates shortly after Apple releases them. It's unclear what impact a win by Apple would have on Psystar, but at the very least it would stop them from issuing these modified updates, leaving their current user base up in the air.