Would you put a QR code to your online profile on a business card?

Sure, why not?  But I would rather embed all the business card info in the QR code (e.g. the VCARD or MECARD formats) and interested parties can add it to their address book in one scan.  QR code readers are increasingly present on smartphones. If the QR code is just a link, then typing it in maybe be just as fast, as Judy pointed out.

It certainly can, but why use the QR code for that? Use the business card for your contact info and the QR code for a special deal, free report, video, or online gallery that will really make an impression on the recipient. Why make them use the QR scanner to get the same info they could just get on the card?

It depends on what industry you're in. Do the people you're handing your cards out to know what a QR code is? If not, I wouldn't bother. Conversely, if you're in a tech industry or marketing, you should make sure whatever online profile you link to via your QR code is mobile-optimized.

You can also use http://napkk.in to create paperless cards on your iPhone/Android that are swappable by QR-scanning. This way, you can use your phone to swap cards and manage contacts without having to carry any paper.

QR codes are a thing of the past. 1, You need to download a QR code reader to scan the code. Smartphones don't have one pre-installed. 2. You need to open the app, take a photo, have the app decipher the image, and finally point you to the website/link. It's a waste of space. You might as well just include your website on your business card because it's probably quicker to type in the url.

We see a lot of business cards printed at http://Printchomp.com. Personally as a marketer, I don't see a lot of value of QR codes. I have done a lot of checking to see if the code is actually used. The reality is a good Google or Siri search trumps QR Codes.

Check out BudFlash, in iTunes or Google Play (Android) App Stores. From http://www.bridgio.com/ It's QR scan based, no need of internet connection. So it's secure, no worries about your contact being uploaded to somewhere without your acknowledgement. Also you can have multiple contact cards for various social scenes.

Why use a QR code? Just another barrier between your business card being used and the user getting your information. I much prefer to know their business email address/URL. I can type it and just get going. No need to scan anything and then take that info from my phone and type it into the computer. If you are going to use a QR code do it as an addition to more standard means of providing your contact info, not as a "cool"/"hip" replacement for it.

I use a MeCard/VCard code on the back of my card, if for no other reason other than it brings up conversation about the use of QR and cross media promotion.