I spoke about this in my glyph wall post and you should be worried about it becoming rampant. As prices drop for herbs (I was buying 5 gold icethorn the other day) you will see people attempting to sell glyphs very low to drive the other scribes off the market. Let's look at the costs for a 5 gold stack of herbs:
6 inks = 6 one ink glyphs
Each glyph costs 83 silver then and an additional 12 silver 50 copper for the resilient parchment. I can therefore sell glyphs above 95 silver 50 copper for a profit.
Imagine if someone posted all glyphs that take one ink to make for 1 gold 50 silver. Just think about how detrimental that would be to the glyph industry. Obviously it would take several people doing it to really make it work, as the glyph industry is just too large for one person to properly control, but if enough people start doing this things could get ugly really fast. The glyph wall is one hell of a weapon :)
What you described is difficult to pull off however, where one toon posts for 50 silver and the next posts for the correct amount. If timed perfectly then your opponents will post all at their fallback rates and you can suffer the minor loss of the 50 silver glyphs selling before the ones at the correct price do, not to mention pick up a bunch of super cheap glyphs to restock your guild bank tabs should they undercut.