EU arbejder i øjeblikket på et sæt love, der vil introducere en ny regelbog for internetgiganter.
Stærkt personlig målretning af webbrugere til annoncering er en central del af internettet i dag, men nogle i EU ønsker at forbyde det, hvilket potentielt hæver en forretningsmodel, der gjorde Google og Facebook til giganter.
Emnet er særligt følsomt for Facebook, som er blevet en af verdens mest profitable virksomheder ved at bryde ny terræn for, hvor tæt individer kunne spores til fordel for annoncører.
Spørgsmålet er et presserende spørgsmål for Silicon Valley-virksomhederne, da EU arbejder på et sæt love, der vil introducere en ny regelbog for internetgiganter.
Deres overvældende greb om onlineannoncering har også tiltrukket antitrust-regulatorernes store interesse hos Europa-Kommissionen, som tirsdag fulgte i Frankrigs fodspor for at se nærmere på Googles praksis på området.
En langvarig udfordring for annoncering kan have en dybtgående effekt på big techs bundlinje:Over 80 procent af Googles omsætning kommer fra annoncer, som genererede 147 milliarder dollars (123 milliarder euro) i salg sidste år. Facebook-annoncer indbragte 84,2 milliarder dollars.
"Jeg håber, at parlamentet ikke vil forbyde reklamer generelt, men mikro-målretning af reklamer burde ikke eksistere," sagde den danske MEP Christel Schaldemose, som er en central aktør i en af de nye love.
"Det burde gøres lettere for en forbruger at sige nej" til mikromålrettet annoncering, sagde Schaldemose til AFP.
'Fuld gang'
Schaldemose står i spidsen for vedtagelsen af loven om digitale tjenester, som sammen med en ledsagelov, loven om digitale markeder, har til formål at omdefinere spillereglerne for tech-giganter.
Forhandlinger er i fuld gang i Europa-Parlamentet og blandt EU's 27 medlemslande om at udarbejde reglerne, hvor noget af det hårdeste lobbyarbejde finder sted omkring annoncering.
"Denne digitale giganters økonomiske og politiske magt er stor, og de kommer ikke til at forblive passive," skrev Tommaso Valletti, tidligere chefkonkurrenceøkonom i EU-kommissionen for nylig.
Critics on both sides of the Atlantic are fighting back with one report from the Norwegian Consumer Council asking for a ban on what it called "surveillance-based advertising".
Backed by BEUC, an EU-wide consumer group, and the Consumer Federation of America, the report released on Wednesday said micro-targeted advertising was the cause of widespread discrimination, consumer manipulation and posed a national security risk.
"Consumers should be free to make up their minds about what they want to do or buy without being constantly watched, coerced, misled or manipulated," said Ursula Pachl, BEUC's deputy director general.
"The EU has a chance to create a fairer digital society by banning surveillance advertising... and we urge decision-makers to do so."
The debate isn't a simple one, with even the tech giants at loggerheads over how online ads should work in the future.
Facebook chief executive Mark Zuckerberg and Apple's Tim Cook have exchanged bitterly on the topic, with the iPhone maker publicly questioning the ethics of tracking users for huge profits.
But Facebook argues that advertising is key to providing for a free internet and that Apple's mega-profits depend on people forking out a lot of money for iPhones.
"Apple's approach is completely different, it's generally charging top dollar for nicely designed hardware increasingly bundled with services as well," said Facebook's vice president for global affairs, Nick Clegg.
Google has gone so far as propose an alternative to tracking—a "privacy sandbox" that does away with the third-party "cookie", the key ingredient for online ad targeting.
'Legitimate concerns'
But even Europeans are unsure about the best way forward for advertising and whether micro targeting or tracking should be completely done away with.
A source at the European Parliament doubted that an outright ban was in the cards, with powerful players, including the governments of Germany and France, not prepared to go so far.
The parliament proposal calls for targeted advertising to clearly become an "opt-in" for users and not something that exists by default when you click to Facebook, Instagram or a site operated by Google's ad technology.
But an opt-in would most likely be a death-knell for ad tracking, which even Facebook acknowledges.
An opinion by French authorities, reported by online news site Contexte, said that while Paris understood MEPs' "legitimate concerns" on the issue, even the "opt-in" was going too far.
It warned that parliament's plan would bring flood of ineffective ads, punish publishers and just leave the tech giants stronger.