Opera has content filtering built in, making it easy to block ads. However, to do so you have to mark the content you want and select to block it. Being lazy, I'd much rather download an addon like Adblock in Firefox that already blocks the known offenders. Is there any way to use Adblock's database in Opera so that I don't have to reinvent the wheel and block each set of ads manually?
You really should not use so many in Opera's built in ad blocker since it searches for every entry if blocked substring is present in the address it is requesting and thus has the complexity O(amount of entries). If you enter about 4k entries there, Opera will slow down like a hell. So it's more like chinese toy swiss knife, mostly made of bronze which looks like real one but breaks as you really use it :)
Ad blocking plugins like Adblock Plus have much smaller complexity. All you have to do is to download such a plugin for Opera (iirc it's called NoAds) and check its settings - subscriptions you need are already there.