Safety and security is of paramount importance on the web no matter where users go.
Use the Web of Trust addon - it's free and works on IE and Firefox and is also soon to be added to Google Chrome:
http://www.mywot.com
There are many users who openly abuse Y!Q&A with links to known malicious / dangerous sites, but there are free tools that users can use to check these links:
Web of Trust as has been mentioned, if using Firefox right click the link and select 'View WOT Scorecard'
http://unmaskparasites.com - This will show if sites have hidden links.
http://www.siteadvisor.com/analysis - Site Advisor, paste the link and also read the comments.
http://www.phishtank.com/index.php - enter the url and see if it is known as a phishing link.
Make use of Hosts files:
http://hosts-file.net - enter the url and search
http://www.mvps.org/winhelp2002/hosts.htm - Hosts Blacklist
When users DO click a link, it is important to CHECK that the site is valid, many scams are increasing so users must have updated antivirus and antispyware as well as a good firewall installed.
Here is a link, quite safe, but what will users do with it?
http://www.freepcsecurity.co.uk/cotojo/ClickMe.jpg
Will you check it or will you click it?
Scam links on Yahoo should be reported and the sources identified and blocked and users removed. Far too many are slipping through with links to SkyDrive and other free sites to host malware.
Links that require Personally Identifiable Information (PII) should be avoided at all times, giving that information leads to spam emails, Identity Theft and in some cases Fraud. The criminals behind many phishing scams and fake programs are very well organised....they want your money and personal information.....THINK TWICE!
Like many others, I take security seriously, and spend many hours helping others to remove the mess from their PC's caused by clicking a bad link and downloading what looks like a great program, but isn't.
Use a program such as KeyScrambler to defeat keyloggers:
http://download.cnet.com/KeyScrambler-Personal/3000-2144_4-10571274.html?part=dl-KeyScramb&subj=uo&tag=button
SnoopFree which monitors for dangerous activities and alerts you to them but uses extremely low resources:
http://www.snoopfree.com
So in a nutshell, check, recheck and check again, update your Operating System with available patches, update security programs regularly and don't be too quick to click a link.
Edit: Have ONE email account to sign up on websites which is with a different username and password, genuine sites will allow you to edit your details and email address.
Plenty of free ones around, use them as 'disposable email' accounts.
If using Firefox use the NoScript addon, if using IE use IE7Pro:
https://addons.mozilla.org/en-US/firefox/addon/722
http://www.ie7pro.com
These will help to enhance your protection against clickjacking and other fraudulent activities.
Also remember that 'Trust Seals' can easily be copied and pasted into web pages, and some can be purchased very cheaply, therefore meaning that not all seals are legitimate even when using an encrypted 'https' site.