So it seems some users have started to provide resteem service in exchange for sbd/steem. This is very similar to advertisements seen on instagram ,twitter or facebook.
However, if you plan to use one, you should always keep in mind Popularity Ratio.
Popularity ratio= Number of followers/ number of following
If this ratio is more than 2 or 3 or even higher it means its a very popular account and it wouldn't be a bad idea using resteem service from them. If however, its 1 or lower it would be very unwise to pay for "resteem service"
Lets take an example,
My good friend on steemit @Scrooger popularity ratio = 816/211=3.86.
Lets take another example
joanaltres popularity ratio = 15993/64786 = 0.2468.
That is way below 1 and this means its not popular account.
Keep this in mind if you ever plan to use any "resteem service".
Hope this was helpful