An article in the Sydney Morning Herald suggests they are. Here's an excerpt.
Online retailers ... can never be sure whether customers are inebriated when they tap the "checkout" icon. One comparison-shopping site, Kelkoo, said almost half the people it surveyed in Britain, where it is based, had shopped online after drinking.
But while reliable data is hard to come by, retailers say they have their suspicions based on anecdotal evidence and traffic patterns on their websites - and some are adjusting their promotions accordingly.
"Post-bar, inhibitions can be impacted, and that can cause shopping, and hopefully healthy impulse buying," said Andy Page, the president of Gilt Groupe, an online retailer that is adding more sales starting at 9 p.m. to respond to high traffic then - perhaps some of it by shoppers under the influence.
On eBay, the busiest time of day is from 6:30 to 10:30 in each time zone. Asked if drinking might be a factor, Steve Yankovich, vice president for mobile for eBay, said, "Absolutely." He added: "I mean, if you think about what most people do when they get home from work in the evening, it's decompression time. The consumer's in a good mood."
Nighttime shopping is growing overall. ChannelAdvisor, which runs e-commerce for hundreds of sites, says its order volumes peak about 8 p.m., and that shoppers are placing orders later and later. In 2011, the number of orders placed from 9 p.m. to midnight increased compared with previous years.
. . .
At QVC, the television shopping channel, traffic and viewers rise around noon, then quiet down until after 7 p.m. Then items like cosmetics and accessories sell briskly. "Call them girl treats — they seem to attract a really strong following once you get past dinnertime," said Doug Rose, senior vice president for multichannel programming and marketing for the company. "You can probably come to your own conclusion as to what's motivating her."
Still, the nighttime spike requires delicacy among retailers: For reasons of propriety, they do not want to be seen as encouraging drunken shopping, and many people who inadvertently buy products in that state would most likely return them at high rates. On the other hand, a happy customer can lead to higher sales.
There's more at the link.
I don't drink to excess, so I can't say this has ever been a problem for me: but looking at many young people today, who seem to think nothing of tossing back a few drinks most evenings, I can see it might be something a vendor would deliberately seek to exploit. Seems kinda seedy to me, but then, I'm old-fashioned that way . . .