Admittedly, sometimes it can be awkward, when I'm hired to photograph an event, and I'm a surprise gift. It's happened twice now. The hosts never respond with What a Fantastic Present I Love It! Instead, they say You Hired A What?? and eye me uncertainly up and down for a moment - I'm something akin to a party crasher I suppose. I stand there with my most inviting yet benign smile (I am good at looking benign) and so far, no-one has objected to my presence. I do notice though, that surprise-gifted subjects ham it up for friend photographers (with their point and shoots) in a way that they don't for me. I get a little envious.
Portrait gifts are a different story. People have time to check out my website, and have time to mentally prepare to be photographed.