While I was playing around with webgl I've made an interesting detection.
The support for available image formats of the toDataURL() function has been increased.

Code :
             Mac          Mac          Mac          Mac          PC           PC           PC           PC           PC
            Chrome       Safari       Opera        Firefox      Firefox      Opera        Safari       Chrome       IE-9
            9.0.597.98   5.0.3        11.01        4 beta 11    4 beta 11    11.01        5.0.3        9.0.597.98   9.0.7930
png         +            +            +            +            +            +            +            +            +
 
jpeg        +            +            +            +            -            +            +            -            +
var. comp.  +            +                        -            -            +            -            -            +            
 
jpeg2000    -            +            -            -            -            -            -            -            -
inc. trans. -            +            -            -            -            -            -            -            -
 
gif         -            +            -            -            -            -            +            -            -
bmp         -            +            -            -            -            -            -            -            -
tiff        -            +            -            -            -            -            -            -            -
targa       -            +            -            -            -            -            -            -            -


Especially Safari provides a wide range of formats on Mac.
The only format that is missing is googles "image/webp" and maybe "image/svg+xml".