Three new companies - Pando Networks, Perenety, and WiredReach - are covered in File-sharing is the new email. Developers are naturally turning to P2P to go beyond the file attachment limits in email.

More on the startups from the article:

Rather than containing the photo and video files themselves, Pando's package just contains information about the location of the files. The recipient gets a link to download Pando's software, which begins downloading the files as soon as it's installed.

Pando uses the same technology found in BitTorrent, a relatively new file-sharing system that's been gaining popularity among the geek set, but which still remains beyond the grasp of the average computer user, according to Samid.

"Our goal was to bring the power of BitTorrent to the mainstream user who just wants to email Mom some heavy photos and videos," he says. So far, the plan seems to be working. The company has more than 315,000 users, with 6,000 signing up every day. They share 15 terabytes of data on an average day.
Preventing piracy

To keep Pando from being used by music and movie pirates, Pando has restricted the number of people to whom you can send a Pando package, and limited the file size to one gigabyte, enough space to hold about 45 7-megapixel photos.

While Pando has tried to keep its application close to the email-attachment model, Perenety has modeled its Shooter application after Skype, the voice-over-Internet-protocol outfit which was bought by eBay (Research), says co-founder Xavier Casanova.

It may seem like an unlikely comparison, but Perenety, which is now conducting a limited test of Shooter, is emulating Skype's one-to-one connectivity and buddy-list features. Just as Skype connects two PCs directly for a call and tells you which people are available to talk, Perenety connects PCs directly for speedier file transfers and lets you know when your contacts share new files.