Yeah be careful. I did this is in a 24-related forum.
I wrote a statement in a spoiler thread saying (and if you know 24, you'll know what I'm referring to), "Jack will throw Paul Raines' (dead) body into Marwan's bunker in an attempt to smoke him out." I thought this was so preposterous that no one would think it could be a real spoiler. Forum regulars knew that I was joking. However, it boomeranged on me when some people actually believed it and quoted it in the official Fox 24 forums as fact. Two seasons later, forum newbies were writing, "I had read that Paul Raines spoiler... what happened to it..." I had to explain that I had written it as a joke every time someone mentioned it. So even if you're speculating or joking (no matter how many smileys you put after it), someone may take your speculation and run with it.