Almost 12 years later, iTunes 4.9 remains an important update for 2 reasons.
I've had my own podcast since 2012, and it's also a huge part of my entertainment consumption. Podcast support in iTunes made it easy to find and download almost 8,000 shows. Prior to that, you had to use a third party program. iTunes brought it mainstream. They made it easy to subscribe and easy to find new shows.
I'm sure that number has grown to many hundreds of thousands in the years following. I have friends who make their living off podcasts. While I don't use iTunes or Apple's podcast app (see what I use), we all owe a lot to Apple taking this category of media to the mainstream. It's an open standard, and a way that anyone can create content.
Odeo Releases Twttr
Had Apple not released iTunes 4.9 with podcasting support, it's possible that Twitter would have never been created. Had Twitter not ever been created, there would be a lot of friends I would have never made. I've also discovered a lot of podcasts via Twitter as well. This all worked out well for everyone involved. While Twitter has its problems, I still think it is a net positive for society.
Here's to 12 years of podcasts and many more. Thank you iTunes 4.9.