Why would anyone think it's a good thing to spam someone else's Twitter timeline promoting their own product? I'll give you an example; one of the ways I've built my Twitter is by following people with similar interests i.e. blogging, social media and health and wellbeing. Maybe some people think that if they have been followed by someone (say me in this instance) that means they can now send a Tweet to their new follower along the lines of "Hi, thanks for following have you checked out my blog yet?" Then they put a link to their blog or product on my timeline. It's infuriating enough when they do this in a Direct Message (DM) but to post on my timeline; that's just rude.
Well actually, no I haven't checked out your blog and because you were so self-promoting on my timeline guess what? Yes, I've unfollowed you! Banned!
Personally I think it's a bad Twitter mistake and a surefire way to piss people off. If you really want someone to look at your blog then treat your new follower as a 'lead' in a sales funnel. All good salespeople know that you don't start promoting your service to someone you have met at a networking event or at a potential client visit. No, no, no, no! You don't do that!
Firstly, you find out about the person you have met: What do they do? What are their interests? What are their obstacles? etc. Why? Quite simply because you can't sell something to someone who has no desire or need for your service or product. Also, by showing a genuine interest in a person, without even thinking of a sale in mind, you are building rapport. Now that person might not need your service or product, but someone they know might. Your new connection might just refer you on to another person.
It's the same with Twitter. Don't automatically think someone needs your product or service. You need to build rapport and show an interest first.
The bottom line is if the 'Twitter Spammer" (in my mind he's a spammer) had actually started a conversation with me, maybe along the lines of "Love your blog; how did you get into blogging?" or something like that, then a conversation starts and who knows, it could eventually lead to a sale, Retweet or a genuine referral.