Something like this doesn't bother me at all. I enjoy using Twitter for free, and as long as the ads are targeted based on what I search for, they can be quite useful.
If they aren't too intrusive (and I doubt they will be), this sounds alright. It's just surprising they haven't done it sooner, which probably shows the ads won't be intrusive. If Twitter were hellbent on making tons of cash as soon as possible, they would've thrown ads all over the place quickly.
Just to make sure you're on the record accurately here, and that your world view is consistent.
You enjoy watching ads on TV, hearing them on radio, reading them on billboards, seeing them on buses, in subways, on milk cartons, benches, ...
It's always OK if it's free, right?
And, they _are_ hell-bent on making cash. Everyone who seriously applies themselves, as they are doing, are hell-bent on making cash. They've acquired a huge base of users who, inexplicably, find value in their wares.
You and those masses are hooked, and now you're advertising targets. Happily so, in your case.
As with Google Adwords (especially PPC ads appearing when I search) this makes sense and, as long as there's a limit to how many ad-tweets appearing at one time, doesn't concern me. After all, if I tweet that I'm headed to Starbucks and get a reminder of their current promotion, that's of potential benefit to me.
Admittedly, the Twitter site itself is far too restrictive to provide me with useful communication data anyway, so I use TweetDeck to track conversations, topics, and mentions. With more real estate, ads would be less cluttering to me.
To the best of my knowledge, they don't even have any significant revenue (besides bigger and bigger VC rounds ;-)) - let alone having hit profitability.
"Once Twitter figures out how to measure the number of people who read posts other than on Twitter.com, it will also allow third-party developers to show ads and share revenue."
Now this is interesting. Twitter 3rd party clients would finally have some sort of business model too!
It's not quite what they've announced, but I think there's potential in the idea that advertisers would pay to promote positive things people are already saying.
There's serious trust/disclosure issues to work out -- burying bad reviews and promoting good ones for payola is what makes Yelp seem a bit slimy. But if advertisers can pay to multiply any little positive thing said by someone real near you, who you already know isn't a professional shill, it could have legitimate influencing power.
Facebook's fan pages are also in an excellent position to try such models, with the same trust/disclosure issues.
I think building that stack that figures out who is saying positive things on twitter about brands is probably valuable in itself. You can resell the results to whomever.
Last summer, I was curious about how Mechanical Turk worked, and signed up for some HITs. I had to classify the sentiment of tweets -- mostly about airlines/airports/travel-in-progress. I suspect I was helping train an automatic classifier. So work on such stacks is certainly underway...
If they aren't too intrusive (and I doubt they will be), this sounds alright. It's just surprising they haven't done it sooner, which probably shows the ads won't be intrusive. If Twitter were hellbent on making tons of cash as soon as possible, they would've thrown ads all over the place quickly.