How much weight on a two-post rack without ceiling support?

[pex]

I can pick this up for 15 bucks if it is available.  In cursory searching, two-post racks seem to generally require mounting, particularly to ceiling, as I guess all racks apparently require floor mounting.

Does anyone have an estimate on what I can get away with using the completely unstabilized rack?  This is just a fun-rack that I don't expect more than 200 lbs to be put on it, which can be placed lowly.  Also, it might be cool to add light shelving higher if the feet of the rack allow for it.

[ricercar]

The tipsy factor depends entirely on the  base of each given rack. That one pictured looks very stable, because there's a rectangular base that extends behind the rack as far as any equipment you're using. No need to secure that to the ceiling unless you put all the weight above the empty rack center of balance. I've mounted a 40 pound disk array 4 feet off the ground, but the array is maybe 18 inches deep, not as deep as most servers.  

You can also hacksaw the rack into two 4-foot racks when it becomes too tall for your experiments. After cutting the rack, the 40 pound disk array serves as the base of the sawed-off top section, and put it all on a $12 wooden wheeled palette from Home Depot.

I'd pay $15 for that rack without blinking. YMMV.