Why is it important to specify your source of funding in published papers and posters? I was reading a paper online, and in a footnote, it read:


  The author is supported by NSF grant DMS-0649473 and by a Simons Investigator Award.


Then it hit me, this information is completely useless to me as a reader. Why would I care what kind of funding the author have? The author for this instance has had every single kind of funding you can imagine, and at no time in my life was I ever interested in knowing any of it. This must be useful information for someone else.

But this is not the only place I see funding information being mentioned. In research posters, you tend to see a list of funding sources being mentioned at the top or the bottom of the poster, like brand names with their own little logos and everything. Again, they are completely meaningless to me. Sometimes I would recognise one of the sources of funding, but there usually isn’t a clear-cut relationship between the fund and the project, especially since a lot of them are government grants.

Can someone explain to me what would motivate one to mention his or her source of funding (or going even further by thanking the fund, award or grant)?
Several reasons.


Conflicts of Interest.  If you're doing climate change research that's funded by The Society of People Who Think Global Warming is Poppycock, you need to mention this. Organizations with a clear interest in a specific outcome are much more likely to produce research that affirms their desired outcome than they do those that refute it, regardless of the actual truth of the matter.  Researchers may perform ethically compromised science to satisfy the funding agency. Since organizational bias (and pressures they exert on their researchers) may not be known until after the fact, this information should always be mentioned so that we can always make the best judgment of the results in light of current knowledge.
Part of the point of funding you is so that the organization's name is out there and associated with (hopefully good) research.  If McDonald's funds your race car, you're expected to put a sticker or something on it with their name on it. Grants often include specific language requiring you to mention the grant in any work that directly utilizes it.
So the grant agency can track work done with their money. These agencies want to know that their money is being used appropriately and for good projects. They don't want to just throw large sums of cash out there willy-nilly.  Money isn't meaningless; it's worth something. This may even be required by law: if they are funded by a government, the government is going to want to know how the money is being used.  Without such tracking, funds can be misappropriated or embezzled, or wantonly wasted on clearly sub-standard proposals.