So Phil had a lot of good ideas for building a list of names. However,as with most social marketing, people catch on to that pretty fast and they are beginning to question the actual "connections" people have on LinkedIn.
I'd recommend a more vetted approach: Add people you like, respect and agree with. If you read an article or blog of interest, Link to the author. If you meet someone at a seminar or meeting whose presentation is in line with your interests, invite them to Link. Another excellent way to find people is to post a Question/Answer on LinkedIn. This lets you know a) how people think and present themselves, and b) if they really utilize LinkedIn for interactions.
It is embarrassing to receive a LinkedIn referral request and finding yourself unable to help the requester because you really don't know the Link very well. Or to have someone ask you for a reference when you've never interacted professionally or personally with your Link.
While I do have a few of those more anonymous Links, they are usually recruiters, so people expect that my interaction with them may be limited.

It is so easy to build a network of hundreds on something like LinkedIn if you reach out to people you've worked with, went to school with, friends, and family. In my initial foray into LinkedIn I accepted some requests from people who I did not know. I figured that building my network was the main goal.

I've taken them out of my network since.

I soon realized that if I wanted an introduction to someone in their network, it would not work because I don't even know them! If I'm getting introduced to someone, I want the go-between to be able to give a truthful recommendation of me.

For me, quality matters on LinkedIn. To reach out to the people a level above me, I go through my network of people who I REALLY know.

Josh Nankivel
pmStudent.com

Great post and comments.

I have grown to like LinkedIn and the possibilities it presents. But i have seen certain users abuse the ability to network by linking to pretty much everyone they have ever known at work, school or elsewhere. The line between LinkedIn and a social networking site such as Orkut becomes blurred.

At times it seems like it's a numbers game - the more contacts i have, the better my networking abilities. I guess some prefer quantity over quality.

I think securing some recommendations from your bosses goes a long way towards making a profile look more credible to potential employers. But going around getting recos from your colleagues and then giving them stellar recommendations in return as a favor doesn't work too well. Smart employers can see right through that.

A while back i noticed that one of the job requirements for a position at LinkedIn required the candidate to have atleast 3 recommendations. So let's get cracking on sucking up to our bosses - past and present :)

I have been a user of linkedin for the last 12 months, and to be quite honest do not find the interface very user-friendly.
What is more, and upsets me most about the site, is that whilst they claim to ban the accounts of people who use it to spam members, i receive between 5 and 20 spam mails a day on my linkedIn account. Once i've managed to sort through all of these messages, i'm then left with a hundred and one approaches from headhunters and vendors all trying to sell me something or sell me to someone.

I found that all of these things inhibited, rather than facilitated my networking with other professionals within my field.

I've now started using a new site called http://www.meettheboss.com which has a far more stringent approach to privacy as all registrations are vetted prior to approval - so no spam, no headhunters and no vendors.