Tasting wine is a subjective business. In the wine trade we try hard to be as objective as possible, but ultimately that's an impossible task. We all have our own preferences for certain styles of wine so naturally we mark the wines we like higher than those we don't.
Knowing what the wines are before you taste them will always influence tasters. Which is why the vast majority of tastings should be conducted 'blind' with the bottles covered.
Tastings should be conducted in silence before everyone confers. People are very easily led so that if one person starts saying flavours out loud they creep into everyone else's notes.The same is true if someone begins to wax lyrical about one of the wines - this will influence others in the room, though the more confident tasters will make a stand and disagree.
The problem is that everyone has very different palates and very different tasting experience. Someone who tastes a lot of wine seriously on a regular basis will have a much clearer idea than an inexperienced taster, or one who doesn't even bother to make notes. Making notes helps you focus on all the different aspects of the wine. This is why it's often hard for tasters to reach consensus on a wine's quality - human beings are simply not objective entities.
Ultimately, it's not possible to be fully objective about anything given our vastly different frames of reference - let alone wine. We are not talking about empirical scientific testing or measurement here - that's simply not possible with wine. The most tasters can do is too agree on how much fruit, acidity, oak and tannin is present in a wine. When it comes to flavours, well my strawberries are your raspberries - it's mainly subjective though in some cases there is a ballpark. It's an odd and intrinsically personal business really.
Like I said - wine tasting is a subjective business!