Interesting concept from iEntry Network appears to be a search engine for Twitter people which categorizes Twitter profiles and shows their last tweet, along with when it appeared (23 hours ago), your city, number of followers and that all important link to your site. That logo though, why does the smiley face (the "O" in Twellow) appear to have a wide-eyed embarrassed appearance, almost as though he were caught doing something inappropriate?
I'd argue for a winking Trickster characterization - who might be saying, "You are only as good as your last tweet." I guess since they now have the name and color scheme suggesting some kind of tie-in with the "Yellow" - it's gonna stay a yellow happy face, but that startled "Oops! You caught me!" look seems to almost suggest people say things they shouldn't on Twitter.
I had to laugh at my categorization too, it appeared under "Food" as well as SEO, I think because I say in my Twitter profile "Eat, Drink, Dream SEO" and it must use your self provided details to categorize people.
iEntry is promoting the site through a house ad in their emailed newsletters, or at least that's how I found it. The database seems to have been building since April as that is when most long-time Twitterers were added to the Twellow site. So the inevitable question of why - or "How do you monetize this?" We have Summize to search tweets, now we can search people at another place.
The site is still being crawled by Google as it only has 288 pages indexed as of this writing - if the entire catalog of users is indexable, it would exceed that little "315,795 people, and counting" in number of pages displayed in the upper right corner and would include more than just the current categories showing in a Google "site" limited search. Could use some SEO as well, since "User Profiles" are currently not showing title tags to match - simply "Twellow.com". At least they aren't putting "NoFollow" on the links to your site at this point. ;-)