It is pretty hard these days not to have a MrSID image behind your vector data. Almost every project I am involved with has a satellite or aerial image behind it. These MrSID images are great because they compress huge raster datasets down to a fraction of their size, but in doing that they cause problems. ArcMap does a great job with MrSID (much better than the old ArcView 3.x ever did) that you almost never notice the difference while panning and zooming, but when you hit that print button the problems begin. The plot file size of these images just balloons to the point of our plotter (HP800ps) just choking on the files. The same plot file using a TIFF is much more manageable. The other big issue with them is you can’t load MrSID into ArcSDE. Well you can, but they don’t work as well as if you had an uncompressed format.
I think the best solution is if you order imagery, always request the “raw” TIFF images as well as MrSID. Down the road you’ll be glad you did.