Their is nothing wrong about it, unless they spam and spam you all the time...

In this context, do you mean "marketers" as data miners and spammers? If so, they should all die. If you mean businesses who want to be...

..more proactive to their customers, then it's very valuable, and Twitter is a better interface than Plurk for them to create a web presence

why you think twitter is better

at least in that regard

I agree that spammers and those who are out solely to sell their products/services should be banned. Too many other venues for that.

one of the things I like about Plurk is the lack of advertising!

I mean businesses who provide real value to real people...

I think there's a way to merge real people with real valuable products/services, but it hasn't been perfected in soc.med. world...