Russ - Excellent points!! You just gave me some food for thought. I would incorporate some of the points you made here.

Well, I'm already using archive.org in determining the age of the site when it is identified as banned in Google.

Anyway, I will try to update it soon, depending I have time to.

IrishWonder - I agree with you on that. "banned" is probably an exaggeration. ;)

Well, don't you think Whois data gives domain name age rather than site age?

www and non-www are normally treated as different domain names by all major SEs, so I did the same.

Well, I must say this that the tool has a lot which can be improved. Let us see when I get time to work on it again.

As for whois data vs web archive data - it really depends. E.g. none of these will show if a domain has been down for a couple years when it changed owners unless you dig deeper, etc., so it's a difficult one best done manually to be most precise. Also, web archive does not add domains right away - it takes time, it's updated from time to time, so it is surely up to you as a developer to decide what data you want to rely upon - but be sure your tool's users realize what is meant by the age of the domain. Whichever you choose would be fine with me but we need to bear in mind that this is just an approximate estimate to show whether or not the domain is not indexed due to its young age or if a ban is likely.

Unfortunately, the banned tool just checks to see if the site is indexed in Google. A better measurement would be to check Yahoo, MSN, and archive.org to determine if the site "should" be indexed already. Many sites appear to be banned when they simply have not been indexed yet. Furthermore, it shows sites that use a robots.txt file to prevent spidering as being banned.