Negative effects? Customized extensions instead of .html, etc

Do these types of customized extensions have a negative effect on rankings?

[onlineshrine]

The Web developers that work with one of my hosting clients want to give them customized extensions for their pages. By this I mean instead of .html or .cfm, etc, they would have .somethingelse.

Will this damage google's ability to index and crawl these pages?

[cayleyv]

I have read that some search engines do not index non standard extensions. So if you wanted to create your own .filename you would be on your own. I dont know the reasoning for this however.

[Imaster]

I have not seen any such examples so far, though I had considered doing this some 2 years back, but didn't deem it smart to play around with SE's.

My recommendation to you would be to use the standard extensions and not play around, unless of course if someone has actually done this before and has seen equal results, if not better.

Good luck onlineshrine.