WordNet (r) 3.0 (2006):

house of cards
    n 1: a speculative scheme that depends on unstable factors that
         the planner cannot control; "his proposal was nothing but a
         house of cards"; "a real estate bubble" [syn: house of
         cards, bubble]
    2: an unstable construction with playing cards; "he built three
       levels of his cardcastle before it collapsed" [syn: house of
       cards, cardhouse, card-house, cardcastle]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "house of cards":
   breakers ahead, bubble, cambric tea, cardhouse, cause for alarm,
   china, cobweb, crisis, danger, dangerous ground, dishwater,
   eggshell, emergency, endangerment, gaping chasm, gathering clouds,
   glass, glass house, gossamer, gruel, hair, hazard, ice,
   imperilment, jeopardy, matchwood, menace, milk and water,
   old paper, parchment, pass, peril, piecrust, pinch, plight,
   predicament, quicksand, reed, risk, rocks ahead, rope of sand,
   sand castle, storm clouds, strait, thin ice, thread, threat,
   water