Shannon of Fox & Prince commented, asking if it's because she asks other bloggers to post an image. That's very smart because it uses viral marketing to advertise the giveaway (and her brand) but that's not the piece de resistance in this particular giveaway.
Look at Sharon's third rule where she asks readers to sign up for her newsletter on her website. This is the biggest winner of the giveaway; not for people who enter, but for Sharon.
Think about who is signing up for the newsletter:
People who really want to have her jewelry
People who want to her from her again and again
People who are (or will become) familiar with her, her products, her shop, and her brand
People who trust her (or are willing to trust her)
**People who are most likely to buy from her.**
Get it? Pretty smart, eh?
By encouraging interested people to sign up for her newsletter, she is building her list of contacts. This valuable list consists of both existing customers and prospective customers. Long after the giveaway is over, she'll continue marketing to this select group of people.
Sending a newsletter is one of the least expensive and most successful marketing tools out there.
It's the most effective way for you to target your marketing information to a receptive audience.
And just in case you are wondering, what Sharon is doing is 100% ethical because she's asking people to opt-in. It's not spammy or underhanded in any way.
I'll let you think about this marketing technique and how you can use a regular newsletter to further market your business to your contacts...