According to sources speaking to Valleywag, Jobs repeated the comments he made during a recent town hall meeting among Apple employees shortly after last month's introduction of the iPad. He reportedly told WSJ staff that Flash is buggy and crashes Macs, is a "CPU hog," and a source of "security holes." He also referred to Flash as dying technology, likening not supporting Flash on the iPad to Apple dropping support for floppy drives, ditching legacy data ports, and replacing CCFL backlighting with LEDs.
Adobe has made efforts to address the concerns about performance on Mac OS X, noting that Flash 10.1 should offer significant improvements (an area we are investigating further). That isn't likely to sway Apple, though, as Jobs recommends replacing Flash-based content with H.264 video, JavaScript, and other techniques. Such a move is doable, if not entirely "trivial" as Jobs suggested.
Source: Arstechnica.com