1A sounds good. I wouldn't recommend going above 1A, because we don't know how wide power traces are elsewhere on the RasPi board, and whatever is the weakest wire will become the fuse. You might consider replacing the 1A polyfuse with a 1A single-blow fuse if you find that the voltage drop across the polyfuse is excessive.
I'm glad to hear your HDMI to VGA is working. If you run into problems, there's good information at the RasPi Wiki here (RGB analog/VGA) and here (Verified Peripherals). For example, some HDMI to VGA converters draw too much current from RasPi and burn out diode D1. If the HDMI to VGA unit you're using works OK, it would help the community if you add it to the Verified Peripherals Wiki if it's not already there.
A hdmi 2 vga converter with it's own power input is recommended.
The hdmi power output indeed passes a diode that can only handle 80 - 100mA. (As John Beetem was also saying)
So that might heat up and produce some magic smoke.
You could short it I guess, but it's there for protection. Other hdmi connected equipment might output 5V on that hdmi pin as well.
So as long as you only connect the hdmi2vga, there shouldn't be a problem when shorting it.
It looks like your hdmi2vga is drawing 100-200mA. SO you might get away with it without roasting that diode.
I just got the element14 WIFI adapter and the HDMI to VGA adapter.
Together they draw too much power when used on the older rev 256K board.
The display blanks off every few seconds or so and the WIFI can't connect. Gets worse the longer it's powered on.
I 'pennied' the fuses F1 and F2 by soldering a wire across them but not much help.
I then shorted across the main fuse F3 and all works fine now.
The original board has a 700mA 'poly' fuse at F3. According the posted schematics the newer Rev 2.0 boards have a 1000mA fuse at F3, and F1, F2 have been eliminated.
I will most likely put in a 1 or 2A poly fuse when I get a chance so the board will not melt down if there is a short.
Hopefully the 1A fuse is good enough on the rev 2.0 boards? Anyone tried my combination on a new board?
Note I am using a 5V 10A regulated switching power supply.