Multiple Domains - Resolve to same IP

Is this considered cloaking?

[NLightN]

I have a client with multiple domains containing a letter, and singular/plural combinations which all resolve to the same IP address. IE:

www.selling4widgets.com

www.sellingfourwidgets.com

www.selling4widget.com

If they all have file extentions for individually optimized pages, will the engines read them as duplicate pages? The content is optimized for keywords and one page is built for each. I'm concerned that the engines will read these as mirror sites and fail to rank them. Any advice is greatly appreciated. Thanks!

[inwaaaytoodeep]

Yoda says:
"Problems there could be if pages were linked across domains yes."