While trying to answer Why static rope rather than webbing for toprope anchors? I immediately thought about splices in long pieces of webbing. For example, REI says that spools of Blue Water webbing may not be continuous, although I cannot find a reference on Blue Water's site.
I haven't worked with spools of webbing in a long time. My recollection is that a spool typically had 3 or so splices that were marked with tape an a pin. We use to cut around them, when making shorter slings. I do not remember how much space we left. My recollection was that apart from the pin/tape, there was no visual indication of the splice.
I cannot find any information about splices. I guess I have 4 related questions.
Do spools of webbing still have splices?
How weak is the splice?
How big is the section of weakness?
What do splices look like?