Several, upon finding that I was married, then asked for the information on my spouse, and auto-filled the spousal last name to be the same as mine. It just struck me as strange, to see Mr. Phizz's first name paired with my last name. It made me just a little bit mad, that they made this assumption that spouses have the same last name.
Then, there was one website that actually HAD NO FIELD AT ALL for putting in the spouse last name. In other words, they had no means for me to indicate that Mr. Phizz and I have different last names. At all. I was like, wtf?
For some reason, this made me really really mad.