Are unofficial offers harmful?

[Meghan Macur]

Several times already, my realtor has called the seller or seller's realtor with our offer price instead of submitting an official offer. It seems like that could be good, in that you get an answer without having to do the paperwork first, and maybe also get a more personal connection with the seller. But I'm also wondering if it makes it easier for the seller to say no to our offer, especially since we are making low offers. Would it be better to submit paperwork that they would have to look at and consider longer?