"The main purpose of this is to allow researchers to study trends and topics during major events, which is something that hasn't really been possible before Twitter gave the world an outlet to express instant views in one single place. So, you might as well go ahead and tweet your thoughts about this; it'll be read in some history book 20 years from now."
I know exactly what they are going to find. We humans are prone to follow residual trends over any situation. Imagine our social communication as one massive hive mind. When an event happens, everyone talks. But we'll end up seeing the most tweets coming from pop culture related news more than anything I think. Like Tiger Woods and Michael Jackson for example. I don't know how the history books will cover that, but I can promise that even when these history books are published our social trends won't have changed.
This is very strange though coming from the legislature. I understand that they are normal people too, but they never really seemed to acknowledge popular culture trends very much. I guess it's easier to archive stuff from Twitter because of the simplicity of the posts. Come to think of it, it makes sense though. When we want to refer back to a place and time in history, we can just look at the responses that millions of people made to get a more accurate data representation of what people actually thought, than trying to make a poll to get an accurate comparison...it just won't work with the polls because not enough people will participate. Skewed data is bad data. Ahem news channels.....
I imagine that we shouldn't have much to fear, unless of course the archive is open to the public. I suspect that people will be safe from possible legal charges as well.