Spammers find more and more ways of spamming us. They exploit social networks like Picasa’s photo sharing service to dig their way past those so-called great spam filters that prevent their potential customers from seeing their messages.
The problem is that you don’t want to report this as spam in your inbox because then legit photo album sharing invitations from your friends and family will be blocked too. On the other hand, this can become a real problem and you will start seeing lots of this sort of spam.
Hopefully e-mail servers will step up and quickly deal with this problem and figure out a verification solution that will make this sort of abuse of their service much more difficult.
It looks like we are going to see more identity verification in the near future. Some way of pre-approving yourself to protect others. With social networks becoming more prevalent you can only expect sites like Picasa to supply you with plenty of spam to keep that social e-mail inbox full of delete clicking delight.