Failing to see the point?
The ecosystem Sony would target to with something like a PSPphone wouldn't be the same for the iBone. The fact that Sony brings up a PS-based phone doesn't mean it is an iPhone imitator. In fact, it has a quite different ecosystem *already in place*, it doesn't need to build it.
1. Sony doesn't *need* a zillion developers for a PSP. Most apps for the PSP would probably be games, which Sony already has a good share of producers churning out. It isn't like N-Gage which needed to bring titles to the platform. iPhone may have more games, but hardcore gamers won't be easily attracted: would you play Pac-Man, or JimBum's "Park-Man" lookalike? Iron Gear Liquid: Snake Biter? hm... I don't think so.
However, I do think Sony would open up to 3rd party developers; in the world of consoles, they were nice enough to allow Linux to run on their PS3s, they are in fact less averse to homebrew stuff as long as they don't hit the game sales income.
2. PSN Store. They've had the Store up there ever since the release of the PS3. The PSP Go even operates on the same principles of the iPhone: buy your games online.
3. This one I don't know, but whatever scheme they're using, it seems to work for game developers.
4. They already have stuff like that for their current SE phones; plus there is the fact that you can simply pass on mp3's on a USB stick to your PS3, or set up media servers on your PC for your PSP & PS3. No need to add a lock-in app.
5. I'd hint a PSPphone would use some modified version of XMB, no need to use something else.
Finally, the "rootkit" which brought such infamy to Sony was actually caused by Sony/BMG ... notice the BMG part.