Tapping up happens all the time in various guises. Gary Lineker says he was tapped up by Tottenham before joining the club (which is hardly surprising given the Venables connection). But there is no evidence that some clubs do it more than others - it's just that some clubs and players are more high profile than others. It's impossible to police - but why is it necessary to do so anyway? If tapping up was not frowned upon, it would become more open and transparent. There wouldn't be so many agents doing clandestine deals, paying bungs and all the other shenanigans which go on.
The "rule" is so antiquated. Players rarely stay with one club these days. Players are always looking to move, agents are always looking to make moves happen and clubs want to know who they can realistically buy and sell at the right price. If there was proper recognition that clubs will covet other clubs' players and players will want to move before their contracts have expired (which is often in the interests of the selling club anyway given the Bosman ruling) , then the process would become more open, less secretive and sleazy and better all round for all concerned. Rather than players handing in transfer requests on deadline day and bungs flying around, there might instead be proper negotiations between clubs, who are both aware that player A has spoken to club B and wants to move. It would work against the bigger clubs because their interest in players is more likely to be flushed out into the open, making it more likely the price will be upped by the selling club or bids will be invited from other clubs.
The irony here is that there is no evidence of tapping up with Kane. Rooney's comments about Kane are interpreted as tapping up because complimenting another club's player is always viewed in that context now. The media then run with the story, Utd confirm they are looking at strikers, any club would want Kane at the right price etc and bingo, Utd are trying to sign Kane despite being linked to 25 other strikers, Bale, Uncle Tom Cobbly and having just signed Memphis Depay! Oh and the Copa America will be the pertfect chance to link Utd with Roberto Firmino, the Brazilian striker too.
