ahh right, good point. Im not sure but I suspect they will be legally fine, line errors are generally pretty obvious. other bookmakers would have very similar odds(but on the correct side) which would legally (I assume) , make it easier to prove the line was in fact an error. Had a dig around bet 365's t&c's and found this. they can be a bit ambiguous at times, but "lines failure" I guess can be construed as a line error. maybe the player would have a better case if the market the error is on, was fairly close, like this fight tonight:
Marcos Rogerio de Lima (1.8)
Clint Hester (2.2)
F. OUR LIABILITY
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just found this too:
6. Errors
6.1 bet365 will not be liable for any errors in respect of bets or wagers including where: (i) there is an Obvious Error in the relevant odds/spreads/handicap/totals/Cash Out amount displayed by bet365; (ii) bet365 continues to accept bets or wagers on closed or suspended markets; (iii) bet365 incorrectly calculates or pays a settlement amount, including where a bet is Cashed Out for the full settlement amount; or (iv) any error occurs in a random number generator or pay tables included, incorporated or used in any game or product.
6.2 Incorrect Price - Prior to the start of an event, In-Play or after the event, where an Obvious Error is identified any bets will stand and be settled at the bet365 revised price. Where a revised price is deemed less than 1/1000 then bets will be void.
Where there is sufficient time before the start of an event, bet365 will endeavour to contact the customer and may in our absolute discretion allow the option of cancelling the bet.
6.3 Incorrect Count/Line/Spread/Handicap/Total - Prior to the start of an event, In-Play or after the event, where an Obvious Error is identified any bets will stand and be settled at the count, line, spread, handicap or total taken at the bet365 revised price except for the following situations:
Like you said it comes down to what they mean by erroneous or palpable/obvious. you could take up a complaint with ibas
http://www.ibas-uk.com/ if it came to that but I think the bookmaker would come out on top still
Also depending on what country the bookmaker is in, laws will be different for lots of them. In the UK the government turns a blind eye to bookmakers consistently targeting and exploiting what adds up to losing bettors and gambling addicts, while simultaneously limiting/blocking accounts of winning punters who sniff an ounce of value on certain lines. it's pretty unethical to not reserve the right for winning bettors to place bets, and yet nothing will be done about it for years. I think in a case like this, the lack of governing laws would probably let the bookmaker get away with it.