No Realtors would try to trick you into such a scam....But if they even tried, they would be out of business in a flash. What probably happened is the property(s) you looked at might have been booby-trapped by whoever posted them on Trulia so if you want more info about those properties, you need to give them your credit card.
Real estate sites are not only the sole target for that genre of scams, you find them into about everything else that even seem to be legitimate businesses.
This is another reason why anyone who is looking for real restate should work with a state licensed real estate professional -- remember that it does not cost you one penny to work with a Realtor. Each state laws of this country state that you are not obligated, in any ways, to even be loyal to one Realtor but we only hope to earn your loyalty to follow trough with us for either handling the sale of your property or the purchase of a new property. Or, use only Realtor.com for accurate real estate searches (no tricks, no scams, no commitments - just accurate real estate information).