So when will Boyd's Maps add layer options for making notations and saving them to an individual profile?
That's something I actually considered once, but decided against it. Lots of work to write an editor with enough options to be useful, and most people wouldn't use it anyway. But there is a screenshot button (camera icon) that gives you a "clean" PNG image without any of the user interface and you can use Photoshop or other software to add notations. Screenshots also include waypoints, so those could be used as rudimentary "annotations" too.
Can you imagine the bandwidth if you covered the entire United States!
I don't think it's a bandwidth issue, it sure would be a storage problem though! The current Northeast US LIDAR elevation dataset covers about 220,000 square miles and consists of 18,335,000 map tiles which use about 600gb of disk space. But there's a companion set of tiles that hold the imagery, which brings the total to about 36.7 million tiles and 1.2 terabytes.
Now, the full continental US is about 3.1 million square miles, which is about 14x the size of the current map (actually, I thought it would be more until I ran the numbers). So, we could estimate that would take around 17 terabytes for the whole continental US at the current resolution of 4 feet/pixel. That's not an outrageous number, but would be a lot more than I could afford - not to mention the amount of time it would take for me to make such a map. I currently have 3tb of disk, which is already pushing the limits of what I can afford for this "hobby"!
The other issue is that I'm pretty sure high-resolution LIDAR DEM is only available for a small fraction of the US. We're kind of "spoiled" here in New Jersey, with full high-res coverage. Other small states are similar (MD, DE, MA, etc). But (just off the top of my head), the 4-foot resolution data is only available for maybe 65% of the current map. If we're talking about the whole US, I'd bet it's only available for 20% or so. Other places would have lower quality DEM, mostly 32-foot resolution with some older LIDAR coverage at around 16-foot resolution.
But, because the whole map must be the same resolution, I'd have to "up-res" that 32-foot data to match the 4-foot data which is very wasteful in terms of storage (a 4-foot resolution map takes 64x more storage space than a 32-foot res map).