Why is onswipe malware? It's irritating, sure, but I'm not sure you can classify it as malware. More of a web design decision.

It's malware because it is typically installed on a blog without the knowledge of the blogger[1], and it frequently crashes the browser by running it out of memory (and even if it doesn't crash the browser, its profligate memory forces other pages out of the cache, greatly degrading the overall iPad browsing experience).

[1] Wordpress made it the default when blogs there are served to iPads. Most bloggers there don't seem to have any idea that iPad users are not getting the theme that the blogger selected.