First off, i love Geni. It has put me in touch with many family members and we now have more than 700 people in our tree, most of which has been viral.
I also like Linked In. Scoble mentioned to me on his blog that he hates linked in and will never go back. However, many of my contacts remain on Linked In and moving them all would be more hassle that it is worth. So while i use Facebook, i'd only start to use it as my main social networking solution IF it was part of a distributed open identity network where i could merge people in there with others in other networks.
However, Linked In has remained fairly static for a long time now. Sure, they have added some features, but they have stood still for so long they have lost ground on other networks that have seen the clear need for something after you have made contact... collaboration, community. Facebook have done very well in that area. FB has also added a "platform" that allows people to build on their services. Linked In could probably take this to the next step by completely opening up and acting as a social network platform for other communities. However, they will have to work fast for this to happen.
So how does this relate in any way to Geni? It's the same thing really, only the connections are family. Once that connection has been made, the major problem on Geni is that there is nothing else to do - not really any tools do make you return after you have connected. I have said in the past they should work with Dandelife (in fact i think Dandelife really need that connection too, but perhaps less than Geni).
At the very least, Geni needs to add family blogging style tools. My daughter said her first word today ... "dada" .. something many of my family would be interested in knowing, along with my video and a few pictures. Geni doesn't really provide any tools to enable that to happen. [ Update (based on Geni Team comment):While I know and have used their image upload and tagging tools which work well, i really mean a diary style tool - the reason blogging has become so popular; this would work really well with a family site and would save me having to "diff" the content of my family tree ] They could probably just provide an option to include external feeds from flickr, youtube, blogger etc and that would be a start.
There is a clear window of opportunity for someone to create what Geni has done, but add the stickiness factor to it. I really think they will need more than just connections... they have such a great opportunity and i love their service, so i hope they start brining some of these things to us soon.