Rough for now, apologies...

OK, requested Adverts on demand from Twitter served as Tweets in the same way adverts are served as adwords.
(ie advertisers buy keywords or phrases but also with a time element - more about time element later...).

Each Tweetadvert is distinguished by (say) a special character or something denoting it is an official twitter advert (ie bought from Twitter the same way you PPC on adwords) therefore trustworthy and genuine, not spam.

Need to use 2 more special reserved characters like the current "@" and "# "(say "?" and "!")... ?subject for request adverts, !subject for end adverts. Advert keywords are joined by underscores.

SPECIAL CHARACTERS

? = the START adverts character
! = the STOP adverts character

Twitter verifies adverts and checks them in exactly the way Google does adwords, ie pretty strict. A campaign is booked by a business and run very much like a Google Adword campaign, in real time except there is an additional "now" time element (see below).

Right here we go...

People only get Twitter adverts if they request them! Absolutely no spam.

Based on Twitter knowing your location. Say you want to fly to Quebec tomorrow, you tweet ?fly_quebec_tomorrow

Twitter has sold the keywords to reputable businesses like Google does, so, it then serves you 20 tweets in the next 2 minutes with flight promotions which are personal and are designed for pretty immediate action (the Twitter USPs). You say "wah! enough adverts". You tweet !fly_quebec_tomorrow and the advert tweets stop.

If you are not at home, the convention could be ?fly_quebec_ny_22082009_not_at_home and then the "not_at_home" will mean Twitter ignores your default location.

Say you are hungry you can tweet ?pizza_now and within 30 seconds, 5 local pizza promotions arrive. Ok, so one says something like "75% off marg+2tops if booked using code 98765 within 3 minutes http://bitly.etc"

I think, WOW that's bloody damn cheap, I will retweet to Mark and Jamie as they might want pizza too. So it gets viralled. But because the time limit it gets viralled urgently. Like "Mark, ORDER NOW!!!!!! Expires in 2 minutes. Wah!"

So the advertiser gets permission based advertising paid at 1 tweet, but due to the re-tweet gets 3 for 1. We all get cheap pizza. We also only get offers WE ASKED FOR.

Not just blatant spam. Twitter adverts could be set to stop as default after 10 minutes. So you just get a blast of them. If you want more, you have another go.

Anything "_now" means you will make immediate (or very fast) decision on the adverts served. (ie you are ready to book the flight online within the next hour, or want to race for a pizza discount). This gives Twitter adverts a USP. I don't think advertisers can get this any other way... maybe texts but that is more awkward and not as virallable or "follower" based.

The advertiser gets 1 to 1 promotions with whatever restrictions they want - time based too, so it can go mad or mental with discounts. Twitter knows who has been previously served, so the next pizza may only be 62.5% discount, etc. and an advert campaign can be based on stunning first offers.

So, as an advertiser I would buy from Twitter "car_leasing" for UK Twitterers at £2.50 per requested tweet (same cost as adwords). I would make my advert Tweets (normal tweet length) very damn good and get web visitors or engage the Twitterer and hopefully viral at no cost to me.

I would buy "car_leasing+now" adverts at a premium and make a landing webpage offer with ummm, free car mats or free £50 fuel (or whatever) if the proposal form arrives within 15 minutes. A McDonalds could target locals with iPhones and when ?food_now is tweeted at around 2:20pm serve the advert "whisper password DOGBREATH at McDonalds Leiceter Square b4 2:30, get FREE lg fries". Would I jog over and whisper "DOGBREATH"? Possibly, yes! People could get creative! Do you see, Twitter could roll out permission based advertising with an URGENCY element.

I would Tweet ?shoes_woman_cool and get several offers for "today only" or "this Saturday 22nd August at whatever local store buy 1 pair get 1 free" and the associated web address would have the store voucher if it is not for online purchase.

I would a) spread the word "try tweeting ? shoes_woman_cool, ruth!" (leaving the space after the "?" would render it useless, Ruth would re-assemble it... or b) say "XXX do great offers, ask for their Tweet ads" or whatever. Advertisers will love it because it is targetted and therefore cannot distress their general market.

Twitter could start to sell these ads, everyone would love them, they are only permission based so no annoyance.

Verdict? Can you improve?