A lot of people have been expressing worry that invasions taking place while hollow will ruin the game for them. Fortunately there's some good news to be had that might allay those fears.
First of all a big thing to consider; if everyone online can be invaded at any time then invasions will be significantly less frequent. Previously you would usually be invaded almost immediately upon becoming human since all those invaders out there were being focused on the small fraction of players who were human at that moment. With that same number of invaders spread across the entire online population there will most likely be significantly more time between invasions. Another important change is that players with more sins will be moved to the front of the line to be invaded. Sins are gained mostly by invading and killing other players. This means that invasions will be focused toward players who choose to engage in PvP, while those less interested will be invaded less.
It's also worth mentioning that it looks like invasions will be much more fair and fun this time around. For many people the main experience with invasions was to be invaded in the undead burg or parish by irresistibly overpowered player who stayed low level but used powerful end-game equipment. Dark Souls 2 is looking to end this in multiple ways. First off players will be matched up not just by level but also by the total amount of souls they've earned. They've also revamped the way stats and equipment interact, like giving stat requirements to heavy armor. The changes they seem to have made to the lock on system and the dedicated servers should also go a long way toward putting an end to those mysterious teleporting backstabs that frustrated so many people.
I understand how a lot of people came to be put off by previous iterations of the system, but I really hope folks will keep an open mind and give it another shot once the game comes out.