I think there is nothing wrong with making connections and sending people messages at all.
Put yourself out there! I do this too.
If you are actively looking for the next career opportunity though, it’s important to make sure you got a good profile with all the relevant information and most importantly a link to your work/website.
I am always surprised how many people don’t put a link to their portfolio into their linkedin profile even though they have one online.
Most of the time I am using LinkedIn for professional updates, announcements and news.
So I would post about new product launches or awards or the like as I can reach the intended target audience very quickly and generate a bit of a profile as a designer for myself.
I have also started posting my Bentobox color boards and it seems like that is being appreciated by the community.
Other than that, I am keeping most if not all my personal stuff out of Linkedin and mainly use Instagram for that.
When it comes to connections, I am pretty open. The only requests I will ignore are obvious sales people, mostly chinese prototypers and moulders.
I think it’s great that we have a dedicated forum for professional information, connections and updates.
It always felt weird posting anything work related on say Facebook. In fact, I have stopped using FB altogether. It’s pretty much only LInkedIn, Tumblr and Instagram for me.