I have noticed that even though in the 80's and 90's a large number of FOCS, STOC, and SODA papers eventually appeared in journals (David Johnson even kindly edited a book that gave pointers to the journal versions of FOCS and STOC papers), the percentage appears to have declined significantly (I have not done a systematic analysis, but when I look for papers I often find that no journal version appeared.)
Most conference papers (even the top conferences) are not reviewed extremely carefully for correctness. The PC has a limited amount of time, and a large volume of papers to review.
What is the reason for this decline?
Are we so desperate to publish papers that we do not want to do a thorough job writing up the proofs after "staking our claim"?
Its very frustrating when when you are reading a paper and details are omitted or missing. Worse still, sometimes claims are made with no proof, or even proofs that are incorrect. Are we not concerned about correctness of results any more? The reviewing process may not be perfect, but at least its one way to have the work scrutinized carefully.
Now that proceedings are on CD's do we still need a strict 10 page limit on the conference version? Is this limit there to simply encourage people to submit to journals? If so, I am not sure its working.
What can we as a community do to ensure that results get properly reviewed and published in full in journals after they are published at a conference?