My wife and I have probably met close to two dozen people from different adult sites. One in particular from Lush.
Have you ever had sex out in a farm field during a rain ?
If I thought said stranger was serious I would probably be right there with you at 80%+ odds of letting them perform oral on me. If I found them interesting and attractive, at least 50/50 odds with a guy and near 100% odds with a woman I'd return the oral.
I like your question, so going to repost that one as mine: If said stranger wanted you to reciprocate (see above two posts), what would be the odds of that happening?