I've been experimenting with some of the newly released features on LinkedIn.
The main focus of the "upgrade" seems to be that you can now search the entire database of 3.3 million LinkedIn users. You then have a choice; you can use "Introductions"... so if I'm connected to Joe, and Joe knows Mary, I can ask Joe to connect me... But 3 degrees is now the limit, so I can reach anyone Mary knows. I just can't go out a level to 4 degrees. Alternatively, I can now upgrade to a business account, and use an "InMail" to someone I don't know, who I've found. The difference with InMail is that it mainly shows up on your homepage for LinkedIn, and, I'm assuming, you get an email notification, too.
There are two pricing models, $15/month, which includes 3 InMails, or $50/month, which includes 10. Basically, you're paying $5 for each email you want to send to someone that you or a contact of yours doesn't know.
It's an intriguing model. For several markets, such as headhunters and VCs, it would definitely be worth the money. It would also be worth the money for key contacts, where 4th degree connections were taking a really long time to get through.
For folks looking to make additional contacts, it probably increases the incentive to have lots of "mega-connectors" as direct connections, hopefully resulting in bigger 3rd level networks.
I'm actually more intrigued at the moment by the "Find Services" tab...It's a good way to see who in your network is in the space you're curious about. If I'm interested in DC lawyers, I can find 15 real estate lawyers, many of them with interesting General Counsel titles.