Not a stupid question, and for anyone else who might be interested:
Any play in the bearings is a bad thing, as you run the risk of damaging your bearing surfaces (which increases the amount of play, which damages your bearing surfaces, and so on...).
Play in the trueness of the wheel is more subjective. If your wheel is only slightly out of true, and there's no noticable slackness or overtightness in the spokes, then you should be OK to carry on riding. If the rim is wobbling all over the place, rubbing against the brakes or frame etc, then get it fixed straight away.