Yes i understood your question. Generally seo providers know about this. How means every time seo providers work for their customers. In that time if they follow same methods means it will not work out. Again they change the strategy of theirs. Recently google update on jan 2011. I hope cleared your doubts
[报价= zelgly2; 15966832]是的,我ç†è§£ä½ 的问题。一般æœç´¢å¼•擎æä¾›è€…知é“这一点。如何æ„å‘³ç€æ¯ä¸€æ¬¡ä¸ºå®¢æˆ·æä¾›æœç´¢å¼•擎优化工作。在这期间,如果他们éµå¾ªåŒæ ·çš„æ–¹æ³•æ„味ç€å®ƒä¸ä¼šå·¥ä½œäº†ã€‚他们冿¬¡æ”¹å˜â€‹â€‹äº†ä»–们的ç–ç•¥ã€‚æœ€è¿‘è°·æŒæ›´æ–°2011å¹´1æœˆã€‚æˆ‘å¸Œæœ›ä½ çš„æ€€ç–‘æ¸…é™¤[/报价] Thank you very much!
Google guideline is just the same but their algorithm is just getting tighter mostly to give a wholesome, ideal results while getting rid of those who go beyond the guideline..