Recently Pictures of Osama Bin Laden Phishing attack is spreading on twitter . Be aware of it. For more details: http://securitybreaching.blogspot.com/2011/08/pictures-of-osama-bin-laden-phishing.html
That's not for the first time. Phishing attacks happen often (not only at Twitter), so usage of any security services is necessary.
Besides a good security program to protect you, its always good to pay attention to the website address that you visit. A website can be duplicated but the website address cannot. I once saw one for Bank of America that looked identical to the banks site but had a completely different name. I immediately reported it.