Well the issue is anti-competition. There isn't much that Palm and apple directly compete with that would be advantageous besides the phone market. That's their only business similarity. Palm does have integration with the Amazon music store But Apple doesn't prevent anyone from accessing its own music or the music from Amazon. What other market would be relevant - the iPod's don't count because they are arguably a secondary market that Palm doesn't engage in.
In order to have anti-trust you have to utilize one monopoly to create another unrelated monopoly. The iPhone is certainly not a monopoly but if it was, its related to iTunes directly. The iTunes store may be considered a monopoly (but only through market share - Apple's tunes can be played back on other players - other companies can exploit that (apple documents it). My point is that there is no real argument of Anti-trust because there no evidence that Apple is doing anything more than limiting the usage of the iTunes software - since it's closed source thats understandable. If there were any claims of anti-trust, Apple can easily argue that its songs are not inherently tied to iTunes and can be uses with any other program that can play them back.
The only monopoly argument that can be made is with the marketplace of iTunes and the popularity of iTunes and the iPhone. But there is nothing illegal about a large market in of itself or having a highly desired product. Unless you can argue that Apple has to publish the iTunes SDK to allow this, the case is moot. Apple doesn't have to open it up. iTunes is just a front end to Quicktime that Apple owns and controls. There is nothing inherently anti-competitive about iTunes other than it comes on Macs - something you expect being that OSX is Apple's software.
Of course you can argue that OSX is anti-competitive, but that has never been successful argued either and would be much tougher to use. In other words, you just can't say "apple is popular, that's unfair" or "Apple's music store is successful and that's not fair!" because they don;t really mean anything.
