What are the consequences of withdrawing an abstract from a conference? I have submitted an abstract for a conference using some preliminary results. I read all the advice about how to write an abstract with no results and I didn't lie in my abstract—I just presented the results I had in hand and discussed the value of the data that I would acquire in the future without making any specific claims about the conclusions I would draw. The abstract deadline was about 6 months before the paper deadline, so I had anticipated acquiring more data that I could write about in the paper and make it a strong contribution. Unfortunately, due to unforeseen circumstances (lab caught on fire, experiment exploded, computer with all my data was wiped by an EMP and velociraptors ate my backups, or some other more mundane reason) the data that I anticipated having is not available and I won't be able to write the full paper.

Many conferences have a "No paper, no podium" and "No podium, no paper" policy, so in those cases one of the consequences of not submitting the paper is that it will not be published in the conference's proceedings and I won't get to present it at the conference. For other conferences, this may vary.

But what are the other consequences (to my career, to future publication of the paper) of withdrawing the paper at this stage, either by not submitting anything or by contacting the program chair and withdrawing?
First, I should mention that the "no paper, no podium" (and vice versa) only applies to conferences where proceedings are published. For many conferences, this is not the case—including many conferences in physics, chemistry, engineering, and applied mathematics that I regularly attend.

In general, if you have to withdraw a paper because of whatever reason—visa issues, experiments not working, or kidnapped by aliens (etc.)—it will not have that much impact on your career. The effect will increase, however, the more papers you withdraw, and the more trouble that you cause the conference organizers as a result. If you let them know well in advance that you're not going to be there, they can try to organize some sort of replacement for you, which, although suboptimal, is better than having a "hole" in the schedule. On the other hand, if you wait until the morning of your talk to withdraw your talk, you will definitely tick off the organizers, which may have an effect on your ability to present in the future (at least at that conference, or others the organizers work on later).