Do eggs have to be very fresh for baking?
Fresh eggs are best when...well, when you want to eat eggs.  However, there has been some dispute about the impact of age in baking situations.  As eggs age, the whites thin.  Some people think that this leads to better elasticity in baked goods...as in, you will achieve a better rise.  However these folks disproved that theory, as cake made with older vs. fresh eggs rose to the same height.
Now, when it comes to meringues, older might be better, as thinner whites lead to better air incorporation, but plenty of people make successful meringue with fresh eggs, and simply allowing the whites to come to room temperature helps a great deal.
Related, and in the case of macarons, I have found nothing definitive.  Is it tradition...is it science?  Many recipes call for separating the eggs and leaving them in the refrigerator for 24 hours before use (some call for leaving on the counter, but I would not recommend this for safety reasons). However, plenty of folks (me included) have made macaron with supermarket eggs, same day, with no problem.  Obviously, those are not &quot;farm fresh&quot; from the chicken.  However, you can find evidence on the internets of people using &quot;farm fresh&quot; eggs.  The issue is related to the point about meringue above.  The difference doesn't appear to be so dramatic, that there is an accepted practice here. One needs to begin with a stable meringue.  There are ways to get there with any egg.
Another consideration is that the flavor of eggs changes with age, and not necessarily in a good way.  So, especially in delicate applications, I would want my eggs to be relatively fresh.