I've seen a few blog posts on the new phenonomon of twitter bombing (here and here). We're all familiar with the google bomb. The twitter bomb, given that twitter is now something of limited universe search engine, apparently is an adaptation of this older tactic. I don't claim to be an expert at this so feel free to jump in and correct anything you read here in the comments section.
Here it is in a nutshell. This is where you search twitter posts, aka "tweets". If I flood twitter from multiple user accounts with the same tweet, such as "Harvard sucks", anyone searching twitter for the words "Harvard" or "sucks" is likely to come across my message. I could further attach a link to my message, such as "Harvard sucks http://www.joe.com". This might get additional traffic to joe.com. It's a form of online guerrilla marketing. The problem with this is that other tweets are continually pouring into the twittersphere and those containing the words Harvard and sucks will degrade my results. The new tweets from outside sources (lacking my link) will push mine out of the search results. It's like trying to swim upstream against a swift current. You can only pull it off for a short burst, if that.
Here is the twist making the tactic more powerful. What if I and my confederates in the twitter bomb use the the one word preceded by a hash mark--"#sucks"? We are presumably the only people out there with tweets using "#sucks" so we own that result but nobody is searching that term. How does this help us? The answer: Trending Topics. Within each twitter user's home page is a section on the right tool bar by this name (see graphic). See the terms with the hash mark in front? Those are twitter bombs. The people behind those bombs have flooded enough tweets using their term into twitter to cause it to show up on the "Trending Topics" section published on every twitter user's home page. If a curious user clicks on the link, they see the full message that can include the link you are promoting.
Someone marketing the candy Skittles recently did a twitter bomb to help with a free promotion for a laptop giveaway. The whole point of the google bomb was to get readers to this product promotion page. I have no idea whether this is a legit promotion or a scam but, hopefully, you get the point.