Just as people searching for a washer on Google are more likely to click on a washer ad, people looking at the #Astronomer stream are more likely to buy a telescope.
That's not the perfect comparison, but Twitter definitely classifies it's users into ad related categories.
You can classify all you want, but my central point was:
If I'm about to buy a washing machine, I would go search on google. I would not go on twitter and tweet "OMGLOLPOP! Gonna buy a washing machine what does every1 (including advertisers) recommend #confused"
So Google get me at the crucial time I'm about to buy something. Twitter don't.
My brother bought a new dishwasher not long ago. He knew for months that he really needed one, and there was circa 2 years that he wanted one.
For considered purchases, there's generally a long period before a clear intention to purchase where people have some awareness of the need. During that period, they're very open to information on products. If they're at a friend's house, they might say, "Hey, how do you like that dishwasher?" And if they see an ad for a dishwasher, they're more likely to pay attention.
Google does very well once people have decided to search. Twitter will be better for getting them before the conscious decision to take action. And it will also be good for the (often long) period between first Google search and actual purchase.
> If I'm about to buy a washing machine, I would go search on google
Actually we've just bought a washing machine in the past week and Google's ads didn't really have anything to do with it.
Selecting a machine took about three months, a combination of searching for user reviews and information about warranty. None of the Google 'ZOMG BUY NOW' ads were in the slightest bit useful for that.
Once we decided to buy, we noticed that all the ads were for big-name stores that don't have outlets where we live; because Google is basing the results on the address of my ISP, 500 miles away...
Just as people searching for a washer on Google are more likely to click on a washer ad, people looking at the #Astronomer stream are more likely to buy a telescope.
That's not the perfect comparison, but Twitter definitely classifies it's users into ad related categories.