It gives users a false sense of security. The average user is far more willing to trust an arbitrary iPhone application than an arbitrary Windows application, do you not agree?
No, I don't really. I don't think those with a high level of technical intelligence will be affected by wall or wall-less, while those with less than moderate TI probably don't even realize that one marketplace has or doesn't have an approval process. So it's equally dangerous, but I don't think moreso.
A walled garden is unquestionably better. It isn't fool proof but it's the same situation as security: you can't make your system completely secure but you can make it more secure than the next guy. The Android store is the next guy.
