I used to work for a company that converted card catalogs to online library databases. Once I was sitting at work when a neighbor of mine ran into a bunch of Russian cards. Since he didn't speak Russian, he couldn't search for the matching records. (In fact, he couldn't even have matched up the words, since the cards were printed in Cyrillic, but online Russian library records are typically transliterated.) Since there were only a handful of Russian cards, I leaned over and helped him match up the records.
Another coworker overheard us talking and delightedly said to me: "Ты говоришь?*"
I paused. "Я не сказала бы что я хорошо говорю, но нимношка, да.†"
He looked at me blankly. "Oh, I don't know what you said."
"Wait, don't you speak Russian?" I replied.
"Uh, no, not really. I can just say a few phrases."
Am I the only one who thinks you shouldn't go around saying "Ты говоришь?" (or "Parlez-vous français" or "Sprechen Sie Deutsch?") if you can't, you know, understand the response?
*Do you speak [Russian]?
†I wouldn't say that I speak well, but a little, yes.