Politicians in the US are quite good at adapting to new lines of communication during their campaign. They’re known to use blogs and now, at least one of them is on LinkedIn!
If Mr. Obama was interested in effectively reaching a certain public (business), he may have found a great way. He’s already received 1185 answers to his question. For LinkedIn users, see answers here. For those in need of an invitation, send me your email address. Mr Obama’s blog also looks pretty good