I think it's disingenuous to blame Sony's marketing instead of the market they've placed their product into. They can only do so much with this product in a landscape that it's leaning toward different experiences. A "killer app" for the hardcore would not make as big a dent as some are suggesting, I don't think.
The PSP lived most of it's life in the post-iPhone world against the strongest handheld the industry has ever seen and it did well enough.
I would still argue that the Vita will wind up somewhere similar to the PSP but likely a little more balanced worldwide. Sony has shown a proven ability to stick to the marathon of building up a struggling console (PSP and PS3) into a stable position and like both of those systems Sony will likely find it's "voice" for the Vita at some point.
The problem is their inability to gauge what the market will bare for price and how long it takes them to find a voice for their products, so their systems recently have stumbled out of the gate and demanded that long term strategy of them.
All this thread really amounts to is another instance of that with the same questions we've heard from both of Sony's previous systems.
Also, I've never suggested the need for a "killer app". There is no such thing. There is a "killer library" or a "killer release list" though and those do move systems. If Sony painted a road map for gamers that showed such a "killer library" was coming and showed enough media to make it feel tangible the perception of the Vita would be entirely different. The sad part is most of those "killer apps" are coming but Sony fails to bundle it into a package for marketing purposes or to show it off appropriately.