Its just a way to create a lead in Marketo, but you have to pick the response in Hootsuite and click create lead in Marketo, then add any other fields to the popup box manually. It's not very useful in my opinion. It would be better to just Export and import
Agreeing with Jamie on this.
Such an integration could provide much more value, such as aggregating social info on the lead and post them to Marketo, including past relevant social network activity that could be posted in a Marketo custom object.