mash-ups and authorship

this article by Jesse Walker discusses the mash up phenonomen in a bit more depth. she attributes the large number of mash ups to the accessability of the technology over the internet. she also mentions political mash ups - the "pauline pantsdown" one that was even played on the radio a few years ago springs to mind.
i like this quote, and think it sums up the situation of bootlegs/mashups on the internet.
"Technically, they are illegal. Practically, they are unstoppable. "
Although this used to be the mentality applied to filesharing (pre napster bust). i guess because mash-ups are created by individuals and not by an identifiable group/website (like filesharing) it is hard to prevent them being made. i would predict that the real deterrent will come from court cases and angry record companies. then again, we have artists like david bowie and INXS encouraging people to create mash ups.. there is obviously no common stance within the industry as to whether they should be outlawed or allowed.