I think there is an important distinction that has been overlooked by the previous answers.

For old questions that have not been touched in a day or two, I agree with the sentiment of the other answers here that one should post what they can even if they don't have time to find all the sources inside. However they should indicate either in the post or in the first comment below it their general source of knowledge (per IsaacMoses's answer) or at least a recognition of the post's incompleteness.

However, for a fresh question that is still at the top of the front page, if you don't have a quality post to produce, then allow someone else who does have the time and/or resources readily available to track down information to take care of it. I definitely feel that we should be much more interested in quality than efficiency (per msh210 "What's the rush?") as in the long run it makes for a more useful site archive and thereby a more useful site. If you really feel that the asker is looking for immediate help OR you think your half answer will greatly help other answers in their writing process, then leave it as a comment on the question (ie "I think the Kaf HaChaim says it is assur" or "I heard a shiur on YU Torah about this; I'll try and track it down"). These comments can help everyone in their research.

In a world where you can't really trust anyone based on personal knowledge, sourced answers are the key to maintaining intellectual rigor and productive discussion. A well written answer encourages new users to return, and a deeper database of information is what can make J.SE such a valuable resource to veterans and random Googlers alike.

I think there is an important distinction that has been overlooked by the previous answers.

For old questions that have not been touched in a day or two, I agree with the sentiment of the other answers here that one should post what they can even if they don't have time to find all the sources inside. However they should indicate either in the post or in the first comment below it their general source of knowledge (per IsaacMoses's answer) or at least a recognition of the post's incompleteness.

However, for a fresh question that is still at the top of the front page, if you don't have a quality post to produce, then allow someone else who does have the time and/or resources readily available to track down information to take care of it. I definitely feel that we should be much more interested in quality than efficiency (per msh210 "What's the rush?") as in the long run it makes for a more useful site archive and thereby a more useful site. If you really feel that the asker is looking for immediate help OR you think your half answer will greatly help other answers in their writing process, then leave it as a comment on the question (ie "I think the Kaf HaChaim says it is assur" or "I heard a shiur on YU Torah about this; I'll try and track it down"). These comments can help everyone in their research.

In a world where you can't really trust anyone based on personal knowledge, sourced answers are the key to maintaining intellectual rigor and productive discussion. A well written answer encourages new users to return, and a deeper database of information is what can make J.SE such a valuable resource to veterans and random Googlers alike.