well to take it a step further, i actually like to buy things in fours. when i have four like items, i have the freedom to do a grouping of three in one part of the room, and reference the shape/color of said items elsewhere with the single piece. and occasionally, it can look nice to break up the menage a trois trick with a grouping of four for a little surprise. in other words....you have options. and you don't have to kick yourself later, which is awkward and unpleasant, for not buying anything else that 'goes' with whatever display item you want to work with. you've got an instant entourage that can roll two, three or four-deep depending on if you're after some symmetry or a three's company sorta feel.
a grouping of grasses that's been moving its way around the house, one room at a time. their missing comrade is by the back door, adding a little [faux] life to the telephone table there.
in the hub's office, three of four egg vases are scattered throughout the bookshelf. humpty and dumpty occupy one cube of the unit while a single sits atop a stack of books. and the fourth is taking a breather in the closet right now, but he'll get his time to shine again soon too.
and then there's G to the power of four....a gaggle of glass bottles filled with scottish water of all things. they're out in full effect since i'm really enjoying the look of the whole set to contrast a grouping of three apples casually placed nearby.
last note for the day....i don't purchase anything + everything in fours. i mean, that could get a little crazy. i've got a chamillion dollar college education in about 18 years to plan for, after all! what i do like to do is snag multiples when the going's good....ie: cheap.
the white top/black bottom vases were $2 each on clearance. the grasses were $8 each, a little steeper, but they're oh-so-flexible with lots of decor schemes. and the agua bottles were $2-ish a piece which was easy to justify considering i can always swig the contents if there's a drought.
so don't go telling your husband later that it was me who told you to buy four rock-tastic tiffany vases. that was all you.
+ + +
if you get a chance, find a copy of the rule of four. i was surprised by how much i enjoyed it!