I am not too concerned about the contact.. The Fermi paradox is still not resolved.
However, the crucial question related to this was already put forward earlier (I think): what could possibly we have that they would want so badly?
It is not resources (ANY un-inhabitable planet or comet or asteroid anywhere in the universe have them)... also I do not think there is any danger of disease or infection (species barrier is not easy to jump over even between organisms evolved here on Earth... the probability of alien organisms that could feed on us is really minuscule, I would say nil. Most likely we would be poisonous to them and vice versa)
The only real danger I can imagine could be their eventual exclusive religious views and motives, if they exist in some form or another and if they are not favourable to other species. This, combined with (possibly) superior technology (if they are visiting us here, they would be superior then) could be fatal.
But, lets resolve the Fermi paradox first
EDIT:
And, yes, "Mote in the God's eye" by Pournelle & Niven is very insightful description of such hypothetical situation.. Read it :-)