I2P does not have stream isolation support which means that visits to Eepsites are linkable and fingerprintable -- each request includes the same X-I2P-Dest* headers, which are unique to each user. This might be true for outproxy requests as well.
If you access site1.i2p followed by site2.i2p, site3.i2p and so on, each one of those operators will see the exact same X-I2P-Dest* values. This means if they are colluding, they will know that the same person accessed all of them.
this is a disaster for alt freaks