Not every device/OS combination can be easily jailbroken. Apple actively fights to keep us out of our own devices, and that has rubbed me the wrong way since I got an iPhone in the summer of 2009. I'll buy an Android or webOS phone next without question.

That we can jailbreak is no consolation for, say, Grooveshark. They put in a lot of work into their iOS app and it's still only available to a relative handful of users on Cydia. It's great we have Cydia but it sucks that you have to join some elite nerd club to use it. Make no mistake, only people who are at least slightly geeky jailbreak devices. Most people cringe at the word "jailbreak" and are scared of bricking their phones. It's a very hard thing to explain to non-technical folk.

Grooveshark focuses instead on other mobile platforms. That's not good for the iOS ecosystem, it's not good for iOS users, and it's not good for Grooveshark. (I can't say that it's not good for Apple because as a result of not having Grooveshark on the store they might be retaining music sales on iTunes.)