HAH. I do actually. I have 3 currently, with room for 4 on my 2 racks.
I was able to use the coupon on my 2nd 40b purchase and got it for $35 + tax.
The limiting factor on these tanks isn't the space actually, it's the OTHER equipment needed to keep things alive in them (Heaters, Filters, Lights) Which is why I've only just started to set up the 3rd 40 (well... that, and available time.)