"Space is a plenty at the garden center."

I think it must depend on the garden center :-) Not all of them have space to spare, especially at this time of year. And it is far easier to cut the vines back than worry about them tangling and possibly damaging each other when they are pulled apart. Many clematis grow fast enough that they easily outgrow a longer stake and the problem returns.

I used to work for a large wholesale grower of clematis and they routinely cut the vines back to avoid this happening, despite the fact they had acres of land!! It doesn't hurt the vines (it actually helps by encouraging additional stemming) and only delays the bloom cycle.

I appreciate the insight, and feel somewhat better. These plants were totally tangled...about 6 or 7 of them must have been like that for quite a while. They could not have been cut back daily as the garden worker stated. I worked a couple of plants apart because I liked the flower. It looks pretty sad, so wish me luck so I can save it. Thanks for your post. Much appreciated.

I'm sure you can save it - clematis are much tougher than they look. If the top growth looks beat up from the untangling, it won't hurt a bit to cut it back. In fact, it is often recommended to cut clems back hard at time of planting but since so many are purchased when they are in bloom, folks are reluctant to do so.