#Twitter: is that a bot following you?

Bots on twitter may be somewhat easy to identify — they use pornographic images for photos and jumbled letters and numbers for names — but blocking them one by one is still a pain.

If you’re at less than a hundred followers (@agold_inews) then it’s not so much of a problem, but if you conduct legitimate business on the site, you’ve likely got something to complain about.

The warnings about bots come shortly after the site became the target of several worms and even a recent scareware infection as malware authors deploy new tools.

Then there’s a new trend, the invasion of Twitter’s trendy topics by spammers, something users are noticing and complaining about.

The spammers jump on these topics and post scary notes next to the key word. Bots are following each other, creating pools of influence. Click on the list of followers of an obvious malware-spewing bot an you’ll find a bunch of images that are Not Safe For Work (NSFW).

This problem won’t “kill” twitter, but it will increase the pain of use, and stunt its growth.

That’s not to say that companies aren’t finding legitimate uses for the service.

Cutting edge data firms like Omniture are finding ways to aggregate and learn from the real time pool of data that is Twitter.

BusinessWeek.com has many of its reporters on Twitter, and some are using it in unusual and innovative ways.