Flash navigation on sites

I often heard that flash is bad. A flash navigation is all the more. Why bad?
The approvers say that the flash navigation is poorly processed by search engines, if the flash is not installed, then the user is deprived, in principle, of the opportunity to work with the site.

Solving the above problems is easy if you use the SWFObject

The idea is that flash navigation replaces the block with the usual non-flash menu.
If the flash is installed, the user sees the flash version of the navigation , and if the flash is not installed, then the normal navigation .