[FoxInSocks]

I wonder how many light bulb manufacturers went out of business in anticipation of the ban?

All of them. From a September 2010 Washington Post article:

"WINCHESTER, VA. - The last major GE factory making ordinary incandescent light bulbs in the United States is closing this month, marking a small, sad exit for a product and company that can trace their roots to Thomas Alva Edison's innovations in the 1870s.

The remaining 200 workers at the plant here will lose their jobs.

<snip>

[E. Pluribus Unum]

I'm sure China has plenty of incandescent light bulb manufacturing capacity to fill our needs.

Perhaps that was the plan all along?