Why, when describing something that has proved unpopular, do people use the phrase "That went down like a lead balloon"?
If you hold them a a little way off the floor most balloons, the plastic/rubber/whatever-it-is-kind, will drop down fairly slowly and gently. If filled with helium or some other lighter-than-air gas, the won't go down at all - at least not straight away. However, if you take a balloon made of lead and let it go it's a fairly safe bet that it would plummet pretty decently... or in other words, go down very well.
English - it's a funny old language.