Well I have accounts at Empire, Party and Eurobet (no funny business with hard-drives etc I opened them all from the same PC and used the same user details and neteller account on each) and, as I only play 10 hrs/week, and already have $1000 in unclaimed bonuses at UB, PS and Paradise racked up, I mostly play the Party sites when they are offering their bonuses. I have just cleared the Empire one and will do the Party one starting tomorrow (I got an email that looks UK player specific). Eurobet's has changed to a monthly $25 for 375 raked hands (hmm it should be $50 I think as the sterling players get £25). I won't bother with that given the other bonuses that I already have lined up.
This is just rational behaviour. Why play without bonus when I have so many bonuses just sitting there ready to earn?
I'm also an attorney and if they are daft enough to start using words like fraud (which is a libel actionable per se in England) they had better not hope to ever bring assets or give prizes out for televised tourneys within the jurisdiction. They will get a libel claim (from someone more litigious than me) and their assets frozen faster than you can call a showdown muppet's all-in.
It may or may not be a breach of their TOS (I didn't read the fine print on accounts on other skins when I signed up) but fraud it certainly ain't...
I do play various MTT's and SnG's on those sites too from time to time and have a non-static IP address so maybe that's why they haven't locked me out yet. To be honest if I could play on just one it would be Party.
I tend to find them the most frantic of sites anyway and prefer PokerPlex and UB for less heart-stopping earnings..