The network response slows down for 10 seconds or so, then suddenly returns to normal, as though someone had stuck a foot on the network garden hose. If you've ever looked at the dots on a printout from an older dot-matrix printer, you can understand the idea of a raster. There's a grid of positions, horizontal and vertical. On other rasters, each XY point can also have other attributes such as intensity and color. The attributes multiply the size of the file by the value possibilities of each attribute.
Color turns mere scanned documents into hard disk pigs.
There are some types of noncharacter data that aren't typically thought of as BLOBs but still qualify. Those include files made from video streams and other data types that need their own timing or are timed together. Data types needing their own timing are referred to as isochronous data. Interrupting an isochronous data stream by normal network events can prevent correctly timed data delivery. Video clip files qualify as BLOBs in some ways, but, in others, they are simply incredibly huge datafiles.