On a zoomed in scale like when showing streets or smaller areas, it doesn't matter.
Students (or whoever else) who might have previously gone to look up a region of the world on a globe, large paper map, or atlas are now turning to sites like Google Maps instead. The market for high quality paper maps has fallen quite a bit as more convenient online maps become the go-to source for answering all sorts of geographic questions.
Moreover, Mercator maps are turning up as the basis for many other tools. For instance, several online map collections have started georeferencing and reprojecting historical maps onto a Mercator projection, saving them as raster tiles, and allowing visitors to pan and zoom around on those reprojected maps, Google-Maps style. Instead of looking at various original maps with region-specific projections, now the viewer is getting more and more exposure to just Mercator maps.
If you look around the web, there are many examples of good maps with reasonable projections, but there are also many many examples of people using the Mercator projection in wholly inappropriate contexts. For example, I see Mercator choropleths of US statistical data quite frequently, which should be using something like an Albers equal-area conic projection instead. (http://bl.ocks.org/mbostock/3734308)
On the bright side, work like the D3 guys (Mike Bostock & Jason Davies) and others have been doing has made it easier than ever to construct nice web maps in all sorts of projections, without shelling out big bucks for fancy GIS software.
If they're looking for a globe replacement, they should use Google Earth instead. (Or click the "Earth" view in Google Maps, which returns satellite footage on a globe.)
Anyhow, I think the “earth” view of Google Maps is a “let’s make something that looks cool in a 2 minute demo” gimmick, not a serious tool. When zoomed out, it adds fake atmosphere, arbitrary static clouds which entirely cover some countries, and silly reflection effects. Its user interface is laggy and glitchy as heck, even on top-of-the-line current hardware. It’s impossible to look at either the arctic or antarctic head-on, as the rotation of the globe is strictly constrained.
More generally, orthographic projections have a place as a reference to compare maps to a view on a 3D globe, but they make it impossible to answer many kinds of questions because they involve severe distortions in any particular view, and it’s impossible to see more than about 40% of the globe at a time. Even a draggable orthographic projection makes it difficult to make inferences about distances, directions, and areas that are easy on a physical globe or on the appropriate flat map. Furthermore, satellite pictures are a wonderful tool sometimes, and a nearly useless tool other times.