As moe has pointed out, you're not going to instantly displace entrenched software, especially in businesses. So, you need a migration path. People already ha

As moe has pointed out, you're not going to instantly displace entrenched software, especially in businesses. So, you need a migration path. People already have bucketloads of documents, and many of them are locked up in bizarre proprietary systems (I'm looking at you, Blackboard!). Some kind of bridge is critical, and email is the prime candidate. I would also figure out some precise user scenarios and workflows, then build a tool tailored for those. If you have clearly defined targets, it should become clear where you can insert a new product. For a great example of how not to do it, look at Google Wave. Wave is fantastic, magically engineered, and has all sorts of way-cool properties. Search, tagging, collaborative editing, document uploading, you name it. I've used it on a three person project, and it was the best documentation/communication tool I've ever used. I love Wave. However, I never use it anymore because it's got some deep problems: Wave depends on everybody using Wave. There's no good way to hook into other services. You're confined to the web client, which is a big turn off for some people. Finally, people don't really understand it. What is it good for? Google's answer is "everything", but that's not really an answer. Using Wave is like being trapped on some technological Galapagos, where everything is cool and exotic but totally detached from the rest of the world. That's the kiss of death, especially when you're a startup looking for traction. That's my two bits. Good luck to you, and congratulations on getting into YC!