I've spent a good chunk of this morning deduping my address book using the Plaxo Super de Duper tool. With 1300 duplicate entries it's a trying and frustrating experience. The Plaxo deDuper is great for small numbers of duplicates, but it's not so good when you have a pile of contacts that need editing.
It needs to:
1) Keep track of work done already, just in case the browser crashes. I just about threw the PC through the Window when IE 7 turned that faded "I'm busy" color after an hour of cranking away.
2) Allow me to simply select and move entries from one duplicate or the other to the final card. The tool isn't good enough at guessing the results, and it's not that easy to change those guesses. Drag and drop came to the web a long time ago. This is a perfect place to use it.
3) Ask for an update while I'm looking at the card in question. Often you will find that people have moved on, and the only valid email address you might have is a gmail address. You know they've moved… now you want to send email asking for an update. I had to resort to making a list as I was going through the dedupe process, and then go back and email people.
4) Give me the ability to delete an obviously dead contact, while in the dedupe tool. I don't want to have to take a second pass through my contacts to do this. See point 3) above.