It has certainly been done before, the the results have probably been mixed. You could ask mods to move this to residents' forum and maybe find someone who could give more insight.
I'd be sure to bear in mind that the ratio of graduates to entry level spots changes every year. For example, if you were graduating this coming '09 year but chose to take a year off and participate in the '10 match instead, you'd be forgoing a year with a nearly 1:1 ratio for a year when there is a projected shortage of entry level spots (making things significantly more competitive for the good spots - and even a spot at all). That's obviously not advisable. On the other hand, if you were to graduate back in 06 and took a year off, the 07 match was possibly a bit less competitive due to lowest grad:spot ratio in a long time with roughly 100 spots going unfilled even after scramble.
There is also the financial reasoning mentioned; you will probably be in a lot of debt, have interest piling up rapidly, and be looking to keep pushing through by the time you reach pod school graduation. Furthermore, unless you have pretty solid grades, "I took a year off after graduation" may very well be interpreted at a residency interview as "I couldn't get any decent program last year and am trying again." Lastly, the point of 4th year clerkships is to prepare you for residency; a year off could make you a bit rusty for boards and the duties you will have as a resident.
If you need a year off, you may consider taking that vacation time before pod school starts, not after.