I think it will be better simply because spammers can sign up for hundreds of Twitter accounts and spam like crazy. When they get booted they just re-sign up. Doing so at app.net means paying $36 bucks, far less likely.
That goes for normal people too, when they pay something they tend to respect it a bit more. Forums have been doing this for years.
Right, but none of that has any effect on your own tweet stream (unless you follow spammers).
If you are talking about searching, the only way search is valuable is if a service gains critical mass, and the only way that happens is if the barrier to entry is low enough that enough users join the service, which will include spammers.
Spammy @mentions is what blocking is for. Also, you don't get @mention notifications if you don't follow them (see settings. may or may not be enabled by default).
You can only DM people where you both follow each other.
I get almost a dozen spam mentions or mentions directed at a misspelled username everyday. That adds a lot of overhead to my usage that get old to the point where I don't even want to read my mentions steam anymore. Certainly less frequently than I used to.
I'm @derek on Twitter, so I have the same issue. If App.net ever got popular, these names would have the exact same issue. So, that's not a compelling reason to switch.
I'm assuming that "spam" is largely either @spam or follow-spam. Also, I suspect that blocking @mention after @mention gets a little old after a while.
Actually, I think the quality of your stream will improve. People value things more if they pay for it. In this case, you pay for being a part of a community. It is expected that people will try to keep/improve the quality of the community.
That goes for normal people too, when they pay something they tend to respect it a bit more. Forums have been doing this for years.