Etiquette question:

I deal with numerous "vendors" on my day-to-day job. I've noticed a few of them are either in my 3rd level referrals, or easily found by searches on their company name. It's amazing how many people I know who are on LinkedIn!

Do you think in a vendor-customer relationship it would be rude to send them an invite seeing you deal with them on a frequent basis? Do you see LinkedIn as being for something like this, or do you see it more for people who work together/know each other on a social level to connect?

PS - Yep it's interesting what you find when you search for Flyertalk! (I have a 3rd level contact who identifies as a Flyertalker, plus of course there are a couple of very interesting LinkedIN FT'ers!)