I like the way how this is addressed at Java Ranch:

##Be Forthright When Cross Posting To Other Sites

...keep in mind that this is not generally in the interests of the posters who might be responding to your posts - those folks may find they've wasted their time. You certainly don't want to annoy those you want to help you, so you might want to make the experience as painless as possible.

The best way to do something like this (without ticking people off) would be to let people know upfront that the crossposting is occurring. This makes the most sense if there's a respectable delay between posting in one forum and another, e.g:

"I posted this question the other day in SomeOtherForum.com [link], but wasn't able to get a good answer, so now I'm asking here..."

A responsible netizen might also post a followup in SomeOtherForum.com letting people there know if a better answer is found.

I like the way how this is addressed at Java Ranch:

Be Forthright When Cross Posting To Other Sites

...keep in mind that this is not generally in the interests of the posters who might be responding to your posts - those folks may find they've wasted their time. You certainly don't want to annoy those you want to help you, so you might want to make the experience as painless as possible.

The best way to do something like this (without ticking people off) would be to let people know upfront that the crossposting is occurring. This makes the most sense if there's a respectable delay between posting in one forum and another, e.g:

"I posted this question the other day in SomeOtherForum.com [link], but wasn't able to get a good answer, so now I'm asking here..."

A responsible netizen might also post a followup in SomeOtherForum.com letting people there know if a better answer is found.