But on Saturday, Fay Morley, the owner of Sydney haberdashery shop Park Lane Haberdashery was delighted when a group of enthusiastic shoppers - organised via Facebook - arrived to inject some energy and revenue into her tiny button and ribbon-filled shop.

The "cash mob" was the brainchild of Katy Plummer, who owns the secondhand bookshop next door, Desire Books.

"I think Mrs Morley is awesome and I can't believe she works six days a week at 99," Ms Plummer said.

The 39-year-old works by the motto: if something's a good idea, don't just think about it, do it. So rather than just pondering an idea to support her fellow Manly shop owner, Ms Plummer sprang into action.

That idea was a "cash mob", with 100 people registering on Facebook.

A cash mob is similar to a flash mob, only with money. A flash mob involves people performing an impromptu and sometimes choreographed dance or performance in front of a surprised audience at an everyday location such as a shopping mall. A cash mob is similar, except the idea is that a group descends on a shop and spends a small amount of money to help the enterprise.

Ms Plummer encouraged people to spend just $5 at Mrs Morley's shop. When Fairfax arrived, there was a queue of people waiting in line to go into the haberdashery store. Trade also appeared brisk at the Desire bookshop, where bright bunting, popcorn and cordial lent a festive air.

"The turnout was amazing, it was such a happy crowd and everyone seemed to be excited to be part of it and part of a community where something like this can happen," Ms Plummer said.

Mrs Morley ordered new stock in preparation and Ms Plummer had also borrowed an urn so Mrs Morley could sell cups of tea in the event the cash mob cleared the shop of stock.

"It was a very nice day and I wasn't exhausted at all. So many kind people came by," said the happy haberdashery shop owner.

Despite her 99 years, Mrs Morley, who has run her store for 17 years, still opens her doors 5½ days a week.

"I lived in the country but when my sister-in-law died suddenly the kids said: 'Why don't you run the shop?'" she explains.

"I don't do that much business, and I don't make the rent but [running the shop] is therapy really because I meet such nice people."

Mrs Morley has no plans to retire and prides herself on allowing customers to buy just one button, if that's all they need.

"I never sell packet stuff. If mum wants just enough elastic for a pair of kids' pants that's fine. Kids are our future and I have to keep things going because it's hard to raise kids. If [what I'm doing] helps, then it suits me [to keep running the shop]."

Plummer came up with an easy way for Mrs Morley to understand how she used Facebook to drum up interest in the cash mob.

"How do you describe Facebook to someone who was a grown up when the [Sydney Harbour] bridge was built? How I explained it was that I'd invited my friends, and they'd invited their friends, who'd also invited their friends," she says.

Cash mobs appear to be a phenomenon that has sprung to life only over the past year. The Cash Mobs Wordpress blog claims the first cash mob was held in Buffalo, New York State, on August 5, 2011, organised by blogger Christopher Smith. He arranged for more than 100 people to cash mob a local liquor store, City Wine Merchant.

Since then cash mobs have taken place across the US and around the world to support local nurseries, bookshops and craft shops, among others.

The rules of cash mobs

• The mob date and meeting location must be announced at least a week in advance via Twitter, Facebook and/or email.

• The amount to spend will not be more than $20, although people can spend more if they wish.

• The business must have products that cost less than $20 for both men and women.

• The business must be locally owned and independently operated.

• The business owner must give back to the community in some way.

• The owner must approve the cash mob before the mob is announced.

• The business must be within one block of a locally owned watering hole.

• Cash mobbers must have celebratory drinks after the successful mob.

• The cash mob will occur during the evening on a weekday or on a weekend.

• Parking or public transportation must be available.

* Source: Wordpress blog Cash Mobs

Follow MySmallBusiness on Twitter @MySmallBusiness