Yes and no!
While Facebook is more flexible and its users are more likely to respond to your direct approach, on Linked In is more difficult.
From my experience, on Linked In is more lucrative to share your problem/issue in a form of a question with details on group's board, where the dynamics of Q&A is much better.
Of course you could address your connections directly or by an email campaign, just don't be aggressive with the approach.
Most important (and the determinant for your addressing way and channel) is your product/service that you offer.
If you think I could be useful, you may reach me by email at bogdins at gmail dot com or by skype at technobogdins.