I feel that this is some of the purpose of Twitter and other similar websites/web apps.
You don't beg your Facebook friends to Digg an article because a lot of those people don't even know what Digg is. Twitter is more of a site that like-minded people get to know each-other, so asking for and giving Diggs/Stumbles/etc. is perfectly fine, as long as it isn't every single update you make.
Yes.
I feel that this is some of the purpose of Twitter and other similar websites/web apps.
You don't beg your Facebook friends to Digg an article because a lot of those people don't even know what Digg is. Twitter is more of a site that like-minded people get to know each-other, so asking for and giving Diggs/Stumbles/etc. is perfectly fine, as long as it isn't every single update you make.
It's ok to do it imo... They still decide for themselfs if they want to do it...